Optical imaging transmitter with brightness enhancement

ABSTRACT

Embodiments describe optical imagers that include one or more micro-optic components. Some imagers can be passive imagers that include a light detection system for receiving ambient light from a field. Some imagers can be active imagers that include a light emission system in addition to the light detection system. The light emission system can be configured to emit light into the field such that emitted light is reflected off surfaces of an object in the field and received by the light detection system. In some embodiments, the light detection system and/or the light emission system includes micro-optic components for improving operational performance.

CROSS REFERENCES TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/506,449, filed on May 15, 2017, U.S. Provisional PatentApplication No. 62/506,437, filed on May 15, 2017, U.S. ProvisionalPatent Application No. 62/506,445, filed on May 15, 2017, and U.S.Provisional Patent Application No. 62/515,291, filed Jun. 5, 2017, thedisclosures of which are herein incorporated by reference in theirentirety and for all purposes.

BACKGROUND

An imager detects light and creates a digital image of a scene based onthat detected light. The image contains a fixed number of rows andcolumns of pixels where each pixel maps to a different field-of-viewwithin the scene. Electronic imagers typically make use ofphotodetectors to convert light into electrical signals. Eachphotodetector is located at a different position on the focal plane andusually corresponds to a single pixel or a component of a pixel in theimage. Electronic imagers can typically be classified as one of twotypes: a passive-illumination imager or an active-illumination imager. Apassive-illumination imager collects ambient light such as sunlightreflected by objects in a scene, whereas an active-illumination imagerilluminates the scene and collects reflected light generated by theactive-illumination imager system itself.

A narrowband imager collects light within a limited wavelength range.This is in contrast to a traditional camera which detects light acrossthe entire visible spectrum or into three different wide, RGB colorbands, each of which may be 100 nm or wider. Narrowband imagers areharder to develop than traditional cameras due to the characteristics ofthe optical filters on which they rely. Optical filters serve to preventsome portion of the electromagnetic spectrum from reaching thephotodetectors. Most narrowband filters rely on thin-film interferenceeffects to selectively transmit or reflect light (such filters are oftenreferred to as dielectric mirrors or Bragg mirrors). The spectraltransmissivity of the narrowband filter depends on the number,thicknesses, ordering, and indices of refraction of the constituentlayers forming the filter. The spectral transmissivity of the filteralso depends upon the angle of incidence of the light upon thenarrowband filter.

Current narrowband imagers have either a small field-of-view or arelimited in their ability to filter wavelength bands narrower than around50 nm. Optical filters are sensitive to the angle of incident lightmaking it difficult to achieve a narrow range of wavelengths. Forexample, an optical filter may accept perpendicular light withwavelength at 940-945 nm and slightly oblique light at a wavelength of930-935 nm. Since most photodetectors in a traditional camera have alarge range of angles of light incident upon them, simply placing anoptical filter in front of them would not actually achieve narrowbandfiltering. Constricting the angle of light incident upon thephotodetector usually requires using a lens with a longer focal length,which constricts the field-of-view of the camera.

Imagers with a wide field-of-view have difficulty in generatinguniformly clear visual images and in making uniform measurements acrossa scene. For example, the pixels at the center of the image may appearbrighter or represent a different wavelength of light compared to thepixels at the scene extremities. A wide field-of-view is desirable forsome applications because it provides better situational awareness. Forexample, a camera-based automotive safety system meant to detectpedestrians around a vehicle might require monitoring in a 360 degreefield-of-view around the vehicle. Fewer wide field-of-view sensors arerequired to do the same job (i.e., generate images of the full 360degree field-of-view) as many narrow field of view sensors, therebydecreasing the system cost.

Narrowband imagers have many applications including geographic mapping,astronomy and in LIDAR (Light Detection and Ranging). Narrowband imagerscan detect characteristic light wavelengths such as those generated byplants with chlorophyll or by elements within stars. Narrowband imagerscan be used, for example, to determine vegetation health or to discoveroil deposits. Optical receiver systems, such as LIDAR, can be used forobject detection and ranging. LIDAR systems measure the distance to atarget or objects in a landscape, by irradiating a target or landscapewith light, using pulses from a laser, and measuring the time it takesphotons to travel to the target or landscape and return after reflectionto a narrowband imager. Other LIDAR techniques, such asphoto-demodulation, coherent LIDAR, and range-gated LIDAR, also rely onthe transmission and reflection of photons, though they may not directlymeasure the time-of-flight of pulses of laser light. For many LIDARapplications, it is beneficial for physical sizes of transmitters andreceivers to small and compact, and at the same time relatively low incost. For applications where objects must be sensed with accuracy atlong distances, it is beneficial to increase or maximize the number ofphotons emitted by the transmitter and reflected back toward thereceiver while keeping laser energy emissions within mandated safetylimits.

Micro-optical systems are systems that include miniaturized, opticalcomponents that are typically between a few micrometers and a millimeterin size. Micro-optical receivers arrayed adjacent to each other aresusceptible to crosstalk. Stray light caused by roughness of opticalsurfaces, imperfections in transparent media, back reflections, etc.,may be generated at various features within the receiver channel orexternal to receiver channel. When multiple receiver channels arearrayed adjacent to one another, this stray light in one receiverchannel may be absorbed by a photosensor in another channel, therebycontaminating the timing, phase, or other information inherent tophotons. Minimizing crosstalk is especially important inactive-illumination systems. Light reflected from a nearbyretro-reflector (e.g. a license plate) may be thousands or millions oftime more intense than light reflected from a distant, dark, lambertiansurface (e.g. black cotton clothing). Thus, the stray light photons froma retro-reflector could vastly outnumber photons reflected from othersurfaces in nearby photosensors if crosstalk is not minimized. This canresult in the inability of a LIDAR system to detect dark objects thatoccupy fields of view near the field of view occupied by aretro-reflector.

SUMMARY

Embodiments of the disclosure provide optical imager systems thatachieve wide field-of-view, narrowband imaging with micro-optic receiverchannel arrays that minimize crosstalk and allow tight spectralselectivity that is uniform across the receiver channel array. Someoptical imager systems according to the disclosure can include a lighttransmission module that provides enhanced spot illumination such that apower level of light returning to a light sensing module is increased,while at the same time improving the spatial resolution of the measuredimage.

In some embodiments, an optical system for performing distancemeasurements includes a bulk transmitter optic, an illumination source,and a micro-optic channel array disposed between the illumination sourceand the bulk transmitter optic. The illumination source includes aplurality of light emitters aligned to project discrete beams of lightthrough the bulk transmitter optic into a field ahead of the opticalsystem. The micro-optic channel array defines a plurality of micro-opticchannels where each micro-optic channel includes a micro-optic lensspaced apart from a light emitter from the plurality of light emitterswith the micro-optic lens being configured to receive a light cone fromthe light emitter and generate a reduced-size spot image of the emitterat a focal point displaced from the emitter at a location between theemitter and the bulk transmitter optic. The micro-optic lens for eachchannel can be configured to receive a light cone from a light emitterand generate a reduced-size real spot image of the emitter at a focalpoint between the micro-optic lens and the bulk transmitter optic. Adivergence of the light cone from the light emitter can be less than adivergence of a light cone from the second optical surface of themicro-optic lens for generating the reduced-size real spot image

In some additional embodiments, an optical system for performingdistance measurements includes a light emission system and a lightdetection system. The light emission system includes a bulk transmitteroptic, an illumination source comprising a plurality of light emittersaligned to project discrete beams of light through the bulk transmitteroptic into a field ahead of the optical system, and a micro-opticchannel array disposed between the illumination source and the bulktransmitter optic. The micro-optic channel array defines a plurality ofmicro-optic channels where each micro-optic channel includes amicro-optic lens spaced apart from a light emitter from the plurality oflight emitters with the micro-optic lens being configured to receive alight cone from the light emitter and generate a reduced-size spot imageof the emitter at a focal point displaced from the emitter at a locationbetween the emitter and the bulk transmitter optic. The light detectionsystem includes a bulk receiver optic configured to receive the discretebeams of light from the field, and an optical assembly having aplurality of micro-optic receiver channels defining a plurality ofdiscrete, non-overlapping fields of view in the field. The opticalassembly includes: an aperture layer having a plurality of discreteapertures arranged along a focal plane of the bulk receiver optic; anarray of photosensors disposed behind the aperture layer; and aplurality of lenses positioned between the aperture layer and the arrayof photosensors.

In certain embodiments, an optical system for performing distancemeasurements includes a stationary housing having an opticallytransparent window, and a light ranging device disposed within thehousing. The light ranging device includes an optical transmittercoupled to a platform. The optical transmitter includes a bulktransmitter optic, an illumination source, and a micro-optic channelarray disposed between the illumination source and the bulk transmitteroptic. The illumination source including a plurality of light emittersaligned to project discrete beams of light through the bulk transmitteroptic into a field ahead of the optical system. The micro-optic channelarray can be disposed between the illumination source and the bulktransmitter optic, and the micro-optic channel array can define aplurality of micro-optic channels where each micro-optic channel caninclude a micro-optic lens spaced apart from a light emitter from theplurality of light emitters with the micro-optic lens being configuredto receive a light cone from the light emitter and generate areduced-size spot image of the emitter at a focal point displaced fromthe emitter at a location between the emitter and the bulk transmitteroptic.

In some embodiments, an optical system includes a bulk receiver opticconfigured to receive light rays originating from a field external tothe optical system, and an optical assembly having a plurality ofmicro-optic receiver channels defining a plurality of discrete,non-overlapping fields of view in the field. The optical assemblyincludes an aperture layer having a plurality of discrete aperturesarranged along a focal plane of the bulk receiver optic, an array ofphotosensors disposed behind the aperture layer, and a non-uniformoptical filter layer configured to allow different micro-optic channelsto measure different ranges of wavelengths. The non-uniform opticalfilter can include a graduated optical filter that gradually increasesin thickness in one dimension, or increases in thickness in a step-wisefashion in one direction such that each channel has a constant opticalfilter layer thickness, but where the thicknesses for differentmicro-optic channels are different.

In some additional embodiments, an optical system includes a bulkreceiver optic configured to receive light from a field external to theoptical system, an aperture layer disposed behind the bulk optic andincluding a plurality of apertures located at a focal plane of the bulkoptic, a lens layer including a plurality of collimating lenses having afocal length, the lens layer disposed behind the aperture layer andseparated from the aperture layer by the focal length, a non-uniformoptical filter layer behind the lens layer, and a photosensor layerincluding a plurality of photosensors. The aperture layer, lens layer,non-uniform optical filter layer and photosensor layer are arranged toform a plurality of micro-optic channels defining a plurality ofdiscrete, non-overlapping fields of view in the field with eachmicro-optic channel in the plurality of micro-optic channels includingan aperture from the plurality of apertures, a lens from the pluralityof lenses, a filter from the filter layer, and a photosensor from theplurality of photosensors and being configured to communicate lightincident from the bulk receiver optic to the photosensor of themicro-optic channel. The non-uniform optical filter layer is configuredto allow different micro-optic channels to measure different ranges ofwavelengths.

In certain embodiments, an optical system includes a bulk receiver opticconfigured to receive light rays originating from a field external tothe optical system, and an optical assembly having a plurality ofmicro-optic receiver channels defining a plurality of discrete,non-overlapping fields of view in the field. The optical assemblyincludes a monolithic ASIC including a processor, a memory, and aplurality of photosensors fabricated in the ASIC, an aperture layerhaving a plurality of discrete apertures arranged along a focal plane ofthe bulk receiver optic, the array of photosensors disposed behind theaperture layer; a plurality of lenses positioned between the aperturelayer and the array of photosensors; and a non-uniform optical filterlayer having different center wavelengths across its structure to allowat least two different micro-optic receiver channels to measuredifferent ranges of wavelengths of light, wherein the aperture layer,plurality of lenses, and non-uniform optical filter layer are formed onthe ASIC such that they form part of the monolithic structure of theASIC.

In some embodiments, an optical system for performing distancemeasurements includes a stationary housing having an opticallytransparent window, a spinning light ranging device disposed within thehousing, a motor disposed within the housing and operatively coupled tospin the light ranging device including the platform, opticaltransmitter, and optical receiver within the housing, and a systemcontroller disposed within the housing, the system controller configuredto control the motor and to start and stop light detection operations ofthe light ranging device. The light ranging device includes a platform,an optical transmitter coupled to the platform, and an optical receivercoupled to the platform. The optical transmitter includes a bulktransmitter optic and a plurality of transmitter channels, eachtransmitter channel including a light emitter configured to generate andtransmit a narrowband light through the bulk transmitter optic into afield external to the optical system. The optical receiver includes abulk receiver optic and a plurality of micro-optic receiver channels,each micro-optic channel including an aperture coincident with a focalplane of the bulk receiver optic, an optical filter positioned along apath of light from the bulk receiver optic and axially aligned with theaperture, and a photosensor responsive to incident photons passedthrough the aperture and the optical filter.

In some additional embodiments, an optical system for performingdistance measurements includes a stationary housing having a base, a topand an optically transparent window disposed between the base and thetop, a spinning light ranging device disposed within the housing andaligned with the optically transparent window, a motor disposed withinthe housing and operatively coupled to spin the light ranging deviceincluding the platform, optical transmitter and optical receiver withinthe housing, and a system controller disposed within the housing, thesystem controller configured to control the motor and to start and stoplight detection operations of the light ranging device. The lightranging device including a platform, an optical transmitter coupled tothe platform, and an optical receiver coupled to the platform. Theoptical transmitter including an image-space telecentric bulktransmitter optic and a plurality of transmitter channels, each channelincluding a light emitter configured to generate and transmit anarrowband light through the bulk transmitter optic into a fieldexternal to the optical system. The optical receiver including animage-space telecentric bulk receiver optic and a plurality ofmicro-optic receiver channels, each micro-optic channel including anaperture coincident with a focal plane of the bulk receiver optic, acollimating lens behind the aperture, an optical filter behind thecollimating lens and a photosensor responsive to incident photons passedthrough the aperture into the collimating lens and through the filter.

In certain embodiments, an optical system for performing distancemeasurements includes a stationary housing having a base, a top and anoptically transparent window disposed between the base and the top, alight ranging device disposed within the housing and aligned with theoptically transparent window, a motor disposed within the housing andoperatively coupled to spin the light ranging device within the housing;and a system controller disposed within the housing, the systemcontroller configured to control the motor and to start and stop lightdetection operations of the light ranging device. The light rangingdevice includes a platform, a plurality of vertical-cavity surfaceemitting lasers (VCSELs) arranged in an array, and an optical receivercoupled to the platform. Each VCSEL in the plurality of VCSELs areconfigured to generate and transmit discrete pulses of light into afield external to the optical system. The optical receiver including abulk receiver optic, a plurality of photosensors, each photosensorcomprising a plurality of single-photon avalanche diodes (SPADs)responsive to incident photons, and an optical filter disposed betweenthe bulk receiver optic and the plurality of photosensors and configuredto allow a band of light to pass through the filter to the plurality ofphotosensors while blocking light outside the band from reaching theplurality of photosensors.

In some embodiments, an optical system for performing distancemeasurements includes a rotatable platform, an optical transmittercoupled to the rotatable platform and comprising a bulk transmitteroptic and a plurality of transmitter channels, an optical receivercoupled to the rotatable platform and comprising a bulk receiver opticand a plurality of micro-optic receiver channels, a motor disposedwithin the housing and operatively coupled to spin the platform, opticaltransmitter, and optical receiver, a system controller mounted to astationary component of the optical system; and an optical communicationlink operatively coupled between the system controller and the opticalreceiver to enable the system controller to communicate with the opticalreceiver. Each transmitter channel includes a light emitter configuredto generate and transmit a narrowband light through the bulk transmitteroptic into a field external to the optical system. Each micro-opticchannel includes an aperture coincident with a focal plane of the bulkreceiver optic, an optical filter positioned along a path of light fromthe bulk receiver optic and axially aligned with the aperture, and aphotosensor responsive to incident photons passed through the apertureand through the filter. The optical communication link can extendbetween the stationary component of the optical system and the rotatableplatform to operatively couple the system controller with the opticalreceiver. The optical receiver can further include a collimating lensbehind the aperture and directly coupled to the optical filter, theoptical filter positioned behind the collimating lens.

In some additional embodiments, an optical system for performingdistance measurements including a rotatable platform, an opticaltransmitter coupled to the rotatable platform and comprising animage-space telecentric bulk transmitter optic and a plurality oftransmitter channels, an optical receiver coupled to the rotatableplatform and comprising an image-space telecentric bulk receiver opticand a plurality of micro-optic receiver channels, a motor disposedwithin the housing and operatively coupled to spin the platform, opticaltransmitter and optical receiver, a system controller mounted to astationary component of the optical system, and an optical communicationlink operatively coupled between the system controller and the opticalreceiver to enable the system controller to communicate with the opticalreceiver. Each transmitter channel includes a light emitter configuredto generate and transmit a narrowband light through the bulk transmitteroptic into a field external to the optical system. Each micro-opticchannel includes an aperture coincident with a focal plane of the bulkreceiver optic, a collimating lens behind the aperture, an opticalfilter behind the collimating lens and a photosensor responsive toincident photons passed through the aperture into the collimating lensand through the filter.

In certain embodiments, An optical system for performing distancemeasurements includes a rotatable platform, a plurality ofvertical-cavity surface emitting lasers (VCSELs) arranged in an arrayand coupled to the rotatable platform, an optical receiver coupled tothe rotatable platform, a motor disposed within the housing andoperatively coupled to spin the platform, the plurality of VCSELs andthe optical receiver; a system controller mounted to a stationarycomponent of the optical system, and an optical communication linkoperatively coupled between the system controller and the opticalreceiver to enable the system controller to communicate with the opticalreceiver. Each VCSEL in the plurality of VCSELs are configured togenerate and transmit discrete pulses of light into a field external tothe optical system. The optical receiver including a bulk receiver opticand a plurality of photosensors, each photosensor comprising a pluralityof single-photon avalanche diodes (SPADs) responsive to incidentphotons.

In some embodiments, an optical system for performing distancemeasurements includes a bulk receiver optic, an aperture layer includinga plurality of apertures, a first lens layer including a first pluralityof lenses, an optical filter layer configured to receive light after itpasses through the bulk receiver optic and pass a band of radiationwhile blocking radiation outside the band, and a photosensor layerincluding a plurality of photosensors, Each photosensor includes aplurality of photodetectors configured to detect photons, and a secondplurality of lenses configured to focus incident photons received at thephotosensor on the plurality of photodetectors. The optical systemincludes a plurality of receiver channels with each receiver channel inthe plurality of receiver channels including an aperture from theplurality of apertures, a lens from the plurality of first lenses, anoptical filter from the optical filter layer, and a photosensor from theplurality of photosensors, with the aperture for each channel defining adiscrete, non-overlapping field of view for its respective channel. Foreach receiver channel in the plurality of receiver channels, there canbe a one-to-one correspondence between the plurality of photodetectorsand the second plurality of lenses in the photosensor for that channel,where each of the lenses in the second plurality of lenses can beconfigured to focus photons on its corresponding lens in the secondplurality of lenses

In some additional embodiments, an optical system for performingdistance measurements includes a light emission system and a lightdetection system. The light emission system including a bulk transmitteroptic and an illumination source. The illumination source including aplurality of light emitters aligned to project discrete beams of lightthrough the bulk transmitter optic into a field ahead of the opticalsystem. The light detection system including a bulk receiver optic, anaperture layer including a plurality of apertures, a first lens layerincluding a first plurality of lenses, an optical filter layerconfigured to receive light after it passes through the bulk receiveroptic and pass a band of radiation while blocking radiation outside theband, and a photosensor layer including a plurality of photosensors.Each photosensor includes a plurality of photodetectors configured todetect photons, and a second plurality of lenses configured to focusincident photons received at the photosensor on the plurality ofphotodetectors. The optical system includes a plurality of receiverchannels with each receiver channel in the plurality of receiverchannels including an aperture from the plurality of apertures, a lensfrom the plurality of first lenses, an optical filter from the opticalfilter layer, and a photosensor from the plurality of photosensors, withthe aperture for each channel defining a discrete, non-overlapping fieldof view for its respective channel.

In certain embodiments, an optical system for performing distancemeasurements including a stationary housing having an opticallytransparent window, a light ranging device disposed within the housingand aligned with the optically transparent window, a motor disposedwithin the housing and operatively coupled to spin the light rangingdevice including the platform, optical transmitter, and optical receiverwithin the housing, and a system controller disposed within the housing.The system controller configured to control the motor and to start andstop light detection operations of the light ranging device. The lightranging device including a platform, an optical transmitter coupled tothe platform, an optical receiver coupled to the platform. The opticaltransmitter including a bulk transmitter optic and a plurality oftransmitter channels, each transmitter channel including a light emitterconfigured to generate and transmit a narrowband light through the bulktransmitter optic into a field external to the optical system. Theoptical receiver including a bulk receiver optic, an aperture layerincluding a plurality of apertures, a first lens layer including a firstplurality of lenses, an optical filter layer configured to receive lightafter it passes through the bulk receiver optic and pass a band ofradiation while blocking radiation outside the band, and a photosensorlayer including a plurality of photosensors. Each photosensor includes aplurality of photodetectors configured to detect photons, and a secondplurality of lenses configured to focus incident photons received at thephotosensor on the plurality of photodetectors. The optical systemincludes a plurality of receiver channels with each receiver channel inthe plurality of receiver channels including an aperture from theplurality of apertures, a lens from the plurality of first lenses, anoptical filter from the optical filter layer, and a photosensor from theplurality of photosensors, with the aperture for each channel defining adiscrete, non-overlapping field of view for its respective channel.

A better understanding of the nature and advantages of embodiments ofthe present disclosure may be gained with reference to the followingdetailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an exemplary passive optical imager system,according to some embodiments of the present disclosure.

FIG. 2 is a simplified diagram of an exemplary light detection systemfor a passive optical imager system, according to some embodiments ofthe present disclosure.

FIGS. 3A and 3B are perspective views of a simplified diagram ofdifferent embodiments of micro-optic receiver layers with graduatedfilter layers, according to some embodiments of the present disclosure.

FIG. 4 is a block diagram of a rotating LIDAR system, according to someembodiments of the present disclosure.

FIGS. 5A-5B are simple illustrations of exemplary implementations ofsolid state LIDAR systems, according to some embodiments of the presentdisclosure.

FIG. 6A-6B are simple illustrations of exemplary implementations ofscanning LIDAR systems, according to some embodiments of the presentdisclosure.

FIG. 7 is an exemplary perspective view diagram showing an embodiment ofa LIDAR system employing a 360 scanning architecture, according to someembodiments of the present disclosure.

FIG. 8 is an illustrative example of the light transmission anddetection operation for a light ranging system, according to someembodiments of the present disclosure.

FIG. 9 is a flowchart illustrating a method of using coded pulses in anoptical measurement system, according to embodiments of the presentdisclosure.

FIG. 10 is a simplified diagram illustrating a detailed view of anexemplary active optical imager system having a wide field-of-view andcapable of narrowband imaging, according to some embodiments of thepresent disclosure.

FIGS. 11-14 are simplified cross-sectional view diagrams of variousexemplary enhanced light emission systems, according to some embodimentsof the present disclosure.

FIGS. 15A-15C are cross-sectional views of simplified diagrams ofexemplary active imager systems having different implementations ofcorrective optical structures for astigmatism, according to someembodiments of the present disclosure.

FIG. 16A is a simplified cross-sectional view diagram of part of a lightdetection system 1600 where there is no cross-talk between channels.

FIG. 16B is a simplified cross-sectional view diagram of part of a lightdetection system 1601 where there is cross-talk between channels.

FIG. 17 is a simplified cross-sectional diagram of an exemplarymicro-optic receiver channel structure, according to some embodiments ofthe present disclosure.

FIGS. 18A-18D are simplified cross-sectional view diagrams of variousaperture layers for a receiver channel, according to some embodiments ofthe present disclosure.

FIGS. 19A-19D are simplified cross-sectional view diagrams of variousspacer structures between the aperture layer and the optical lens layerfor a receiver channel, according to some embodiments of the presentdisclosure.

FIGS. 20A-20G are simplified cross-sectional view diagrams of variousoptical filter layers for a receiver channel, according to someembodiments of the present disclosure.

FIGS. 21A-21K are simplified cross-sectional view diagrams of variousphotosensor layers with diffusers for a receiver channel, according tosome embodiments of the present disclosure.

FIGS. 22A-22I are simplified cross-sectional view diagrams of varioushemispherical receiver structures for a receiver channel, according tosome embodiments of the present disclosure.

FIGS. 23A-23E are simplified cross-sectional view diagrams of variousbottom micro lens layers for a receiver channel, according to someembodiments of the present disclosure.

FIGS. 24 and 25 are simplified cross-sectional view diagrams ofexemplary receiver channels, according to some embodiments of thepresent disclosure.

FIGS. 26-30 are simplified top view diagrams of exemplary micro-opticalreceiver arrays, according to some embodiments of the presentdisclosure.

DETAILED DESCRIPTION

Some embodiments of the disclosure pertain to optical imager systemsthat can generate an image from ambient light in a field and/or lightemitted from an optical transmitter that has reflected off of an objectin the field. For instance, in some embodiments an optical imager systemcan be a passive system that does not actively illuminate a scene orgiven area and instead detects ambient light in the scene or areareflected off of one or more objects in the scene or area. A passiveoptical imager system can include a light sensing module for receivingambient light in the field. The light sensing module can be a widefield-of-view, narrowband optical imaging system (WFNBI) that collectsimaging information. The light sensing module can include one or morebulk receiver optics, a micro-optic receiver system, and a systemcontroller for operating the light sensing module. According to someembodiments of the present disclosure, the micro-optic receiver systemcan include one or more micro-optic receiver layers and one or morephotosensors, each photosensor can include one or more photodetectorsthat can measured received light.

A bulk imaging optic as defined herein can be one or more opticalsurfaces, possibly including multiple lens elements, that have clearapertures greater than one millimeter and that is positioned to receivelight projected from, or focus received light on, a micro-optictransmitter/receiver layer. A bulk imaging optic that projects lightreceived from an optical emitter, such as a micro-optic transmitterlayer, is sometimes referred to herein as a bulk transmitter optic or asan output bulk imaging optic. A bulk optic layer that focuses lightreceived from a field onto an optical detector, such as a micro-opticreceiver layer, is sometimes referred to herein as a bulk receiver opticor as an input bulk imaging optic. An input, image-space telecentricbulk imaging optic allows the system to measure narrowband lightuniformly over a wide field-of-view (FOV). The micro-optic receiverlayer can include a one- or two-dimensional array of micro-opticreceiver channels where each micro-optic receiver channel has multiplecomponents including one or more of an aperture, a collimatingmicro-lens, an optical filter, and a photosensor. In some instances, themicro-optical receiver channel structure has a columnar arrangement withenclosures having absorbent and/or reflective side walls and/or focusingfunnels. The micro-optic receiver channel maximizes the collection ofincoming rays through its aperture, collimates the light to make itperpendicular to the optical filter, and minimizes crosstalk withadjacent micro-optic receiver channels due to mixing of inputs fromneighboring apertures, as will be discussed in detail below. In variousinstances, bulk imaging optics according to the present disclosuremodify light or other radiation for an entire array of emitters orphotosensors. Micro-optic structures can be included as part of thearray and can modify light differently for different emitters and/orphotosensors in the array. In some embodiments, there is one or moremicro-optic elements for each individual array element (photosensorand/or emitter).

In some embodiments, the optical imager system can be an active systemthat can emit light into a field and then detect the emitted light afterit has reflected off surfaces of an object in the field. An activeoptical imager system can include a light transmission module inaddition to a light sensing module, and be configured as a light rangingdevice. The light transmission module can include a transmitter layerthat is composed of an array of individual emitters where each emittercan be paired with a corresponding micro-optic receiver channel in thelight sensing module, or it can be a uniform illuminator that spreadslight evenly across the scene with no specific pairing betweenindividual emitters and receiver channels. In some instances, the lighttransmission module can include a micro-optic transmitter channel arrayto enhance light outputted from the array of emitters. During operation,light outputted by the array of emitters (e.g., laser pulses) passesthrough the micro-optic transmitter channel array and enters a bulktransmitter optic having a large numerical aperture to better capturelight from the micro-optic transmitter channel array. The light thenexits the bulk transmitter optic and illuminates a plurality of spots ata distant field. The micro-optic transmitter channel array can improvethe brightness of beams emanating from the bulk transmitter optic toprovide enhanced spot illumination, while at the same time improving thespatial resolution of the measured image, as will be discussed in detailfurther herein.

According to some embodiments of the present disclosure, the imagersystem is a wide field-of-view, narrowband optical system. Thus, theimager can capture images and detect light across a FOV of at least 10degrees. In certain embodiments, the imager can capture images anddetect light across a FOV of at least 20, and across a FOV of at least30 degrees in some embodiments. Furthermore, the imager can detect lightat a wavelength of approximately 10 nm or less. In some particularembodiments, the light sensing module can detect light at a wavelengthof approximately 5 nm or less. In some embodiments, the imager systemcan capture detect light at a wavelength of less than 5 nm across a FOVof approximately 32 degrees. The FOV can be in the vertical orhorizontal direction, or any other angle in between.

To better understand the function and configuration of passive andactive optical imager systems according to embodiments of thedisclosure, each will be discussed in detail herein.

I. Passive Optical Imager Systems

A passive optical imager system receives ambient light to generate animage. FIG. 1 is a block diagram of an exemplary passive optical imagersystem 100, according to some embodiments of the present disclosure.Passive optical imager system 100 includes a passive light capturingdevice 102 for capturing light existing within a field. Passive lightcapturing device 102 can include a system controller 104 and a lightsensing module 106. Imaging data can be generated by passive lightcapturing device 102 by receiving light existing in a field in whichpassive optical imager system 100 is positioned. The received light canbe light that exists naturally in the field, i.e., ambient light, asopposed to light emitted from a transmitter within system 100.

Light sensing module 106 can include a sensor array 108, which can be,e.g., a one-dimensional or two-dimensional array of photosensors. Eachphotosensor (also just called a “sensor” or sometimes referred to by oneskilled in the art as a “pixel”) can include a collection ofphotodetectors, e.g., SPADs or the like, or a sensor can be a singlephoton detector (e.g., an APD). Light sensing module 106 includes anoptical sensing system 110, which when taken together with sensor array108 can form a light detection system 112. In some embodiments, opticalsensing system 110 can include a bulk receiver optic 114 and opticalcomponents 116, such as an aperture layer, a collimating lens layer andan optical filter, that can be combined with sensor array 108 to form anarray of micro-optic receiver channels where each micro-optic receiverchannel measures light that corresponds to an image pixel in a distinctfield of view of the surrounding field in which system 100 ispositioned. Further details of various embodiments of micro-opticreceiver channels according to the present disclosure are discussed indetail in conjunction with FIGS. 17-30 below.

In some embodiments, sensor array 108 of light sensing module 106 isfabricated as part of a monolithic device on a single substrate (using,e.g., CMOS technology) that includes both an array of photosensors, aprocessor 118, and a memory 120 for signal processing the measured lightfrom the individual photosensors (or groups of photosensors) in thearray. The monolithic structure including sensor array 108, processor118, and memory 120 can be fabricated as a dedicated ASIC. In someembodiments, optical components 116 can also be a part of the monolithicstructure in which sensor array 108, processor 118, and memory 120 are apart. In such instances, optical components 116 can be formed, e.g.,bonded (non-reversibly) with epoxy, on the ASIC so that it becomes partof the monolithic structure, as will be discussed further below. Asmentioned above, processor 118 (e.g., a digital signal processor (DSP),microcontroller, field programmable gate array (FPGA), and the like) andmemory 120 (e.g., SRAM) can perform the signal processing. As an exampleof signal processing, for each photosensor or grouping of photosensors,memory 120 of light sensing module 106 can accumulate detected photonsover time, and these detected photons can be used to recreate an imageof the field.

In some embodiments, the output from processor 118 is sent to systemcontroller 104 for further processing, e.g., the data can be encoded byone or more encoders of the system controller 104 and then sent as datapackets to user interface 115. System controller 104 can be realized inmultiple ways including, e.g., by using a programmable logic device suchan FPGA, as an ASIC or part of an ASIC, using a processor 122 withmemory 124, and some combination of the above. System controller 104 cancooperate with a stationary base controller or operate independently ofthe base controller (via pre-programmed instructions) to control lightsensing module 106 by sending commands that include start and stop lightdetection and adjust photodetector parameters. In some embodiments,system controller 104 has one or more wired interfaces or connectors forexchanging data with light sensing module 106. In other embodiments,system controller 104 communicates with light sensing module 106 over awireless interconnect such as an optical communication link.

Passive optical imager system 100 can interact with a user interface115, which can be any suitable user interface for enabling a user tointeract with a computer system, e.g., a display, touch-screen,keyboard, mouse, and/or track pad for interfacing with a laptop, tablet,and/or handheld device computer system containing a CPU and memory. Userinterface 115 may be local to the object upon which passive opticalimager system 100 is mounted but can also be a remotely operated system.For example, commands and data to/from passive optical imager system 100can be routed through a cellular network (LTE, etc.), a personal areanetwork (Bluetooth, Zigbee, etc.), a local area network (WiFi, IR,etc.), or a wide area network such as the Internet.

User interface 115 of hardware and software can present the imager datafrom the device to the user but can also allow a user to control passiveoptical imager system 100 with one or more commands. Example commandscan include commands that activate or deactivate the imager system,specify photodetector exposure level, bias, sampling duration and otheroperational parameters (e.g., emitted pulse patterns and signalprocessing), specify light emitters parameters such as brightness. Inaddition, commands can allow the user to select the method fordisplaying results. The user interface can display imager system resultswhich can include, e.g., a single frame snapshot image, a constantlyupdated video image, and/or a display of other light measurements forsome or all pixels.

As mentioned herein, one or more components of optical sensing system110 can be part of a monolithic structure with sensor array 108,processor 118, and memory 120. For example, an aperture layer,collimating lens layer, and an optical filter layer of opticalcomponents 116 can be stacked over and bonded with epoxy to asemiconductor substrate having multiple ASICs fabricated thereon at thewafer level before or after dicing. For instance, the optical filterlayer can be a thin wafer that is placed against the photosensor layerand then bonded to the photosensor layer to bond the optical filterlayer with the photosensor layer to have the optical layer form part ofthe monolithic structure; the collimating lens layer can be injectionmolded onto the optical filter layer; and, the aperture layer can beformed by layering a non-transparent substrate on top of a transparentsubstrate or by coating a transparent substrate with an opaque film.Alternatively, the photosensor layer can be fabricated and diced, andthe optical filter layer, collimating lens layer, and the aperture layercan be fabricated and diced. Each diced photosensor layer and opticallayers can then be bonded together to form a monolithic structure whereeach monolithic structure includes the photosensor layer, optical filterlayer, collimating lens layer, and the aperture layer. By bonding thelayers to the ASIC, the ASIC and the bonded layers can form a monolithicstructure. The wafer can then be diced into devices, where each devicecan be paired with a respective bulk receiver optic 114 to form lightsensing module 106. In yet other embodiments, one or more components oflight sensing module 106 can be external to the monolithic structure.For example, the aperture layer may be implemented as a separate metalsheet with pin-holes. A more detailed view of an optical sensing systemand a sensor array according to an embodiment of the disclosure isdiscussed herein with respect to FIG. 2.

FIG. 2 is a simplified diagram of an exemplary light detection system200 according to some embodiments of the present disclosure. Lightdetection system 200 can be representative of light detection system 112discussed above with respect to FIG. 1. Light detection system 200 caninclude an optical sensing system and a sensor array. The opticalsensing system can include bulk receiver optics, an aperture layer, acollimating lens layer, and an optical filter layer; and the sensorarray can include an array of photosensors, where each photosensor caninclude one or more photodetectors for measuring light. According tosome embodiments, these components operate together to receive lightfrom a field. For instance, light detection system 200 can include abulk receiver optic 202 and a micro-optic receiver (Rx) layer 204.During operation, light rays 206 enter bulk receiver optic 202 frommultiple directions and gets focused by bulk receiver optic 202 to formlight cones 208. Micro-optic receiver layer 204 is positioned so thatapertures 210 coincide with the focal plane of bulk receiver optic 202.In some embodiments, micro-optic receiver layer 204 can be aone-dimensional or two-dimensional array of micro-optic receiverchannels 212, where each micro-optic receiver channel 212 is formed of arespective aperture 210, collimating lens 214, and photosensor 216positioned along the same axis in the direction of light flow, e.g.,horizontal from left to right as shown in FIG. 2. Furthermore, eachmicro-optic receiver channel 212 can be configured various ways tomitigate interference from stray light between photosensors, as will bediscussed further herein. During operation, each micro-optic receiverchannel 212 measures light information for a different pixel (i.e.,position in the field).

At the focal point of bulk receiver optic 202, light rays 206 focus andpass through apertures 210 in an aperture layer 211 and into respectivecollimating lenses 214. Each collimating lens 214 collimates thereceived light so that the light rays all enter the optical filter atapproximately the same angle, e.g., parallel to one another. Theaperture and focal length of bulk receiver optic 202 determine the coneangle of respective light rays that come to a focus at aperture 210. Theaperture size and the focal length of collimating lenses 214 determinehow well-collimated the admitted rays can be, which determines hownarrow of a bandpass can be implemented in optical filter 218. Apertures210 can serve various functions during the operation of light detectionsystem 200. For instance, apertures 210 can (1) constrain the pixel FOVso it has tight spatial selectivity despite a large pitch at thephotosensor plane, (2) provide a small point-like source at thecollimating lens's focal plane to achieve tight collimation of raysbefore passing through the filter, where better collimation results in atighter band that can pass through the filter, and (3) reject straylight.

Optical filter 218 blocks unwanted wavelengths of light.Interference-based filters tend to exhibit strong angle dependence intheir performance. For example, a 1 nm wide bandpass filter with acenter wavelength (CWL) of 900 nm at a zero-degree angle of incidencemight have a CWL of 898 nm at a fifteen-degree angle of incidence.Imaging systems typically use filters several tens of nanometers wide toaccommodate this effect, so that the shift in CWL is much smaller thanthe bandpass width. However, the use of micro-optic layer 204 allows allrays to enter optical filter 218 at approximately the same angle ofincidence, thus minimizing the shift in CWL and allowing very tightfilters (e.g. less than 10 nm wide) to be used. Photosensor 216generates electrical currents or voltages in response to incidentphotons. In some embodiments, optical filter 218 is uniform across theentire array of micro-optic receiver channels 212 so that eachindividual micro-optic receiver channel 212 in the array receives thesame range of wavelengths of light.

In some embodiments, photosensors 216 are positioned on a side oppositeof collimating lenses 214 so that light rays 206 first pass throughcollimating lenses 214 and optical filter 218 before exposing onphotosensors 216. Each photosensor 216 can be a plurality ofphotodetectors, such as a mini-array of multiple single-photon avalanchedetectors (SPADs). An array of mini-arrays of SPADs can be fabricated ona single monolithic chip, thereby simplifying fabrication. In somealternative embodiments, each photosensor 216 can be a singlephotodetector, e.g., a standard photodiode, an avalanche photodiode, aresonant cavity photodiode, or another type of photodetector.

In some other embodiments, optical filter 218 is non-uniform. Forexample, a graduated filter allows different micro-optic channels tomeasure a different range of wavelengths. In other words, a graduatedfilter allows different micro-optic channels in an array of micro-opticchannels to have different center wavelengths (CWL). A graduated filtertypically gradually changes the range of allowed wavelengths in eitherone or two dimensions. However, a graduated filter could also encompassa filter where the range of allowed wavelengths changes rapidly (e.g.,step-wise) in one or both dimensions. The different CWLs for thechannels can be created in various ways. For instance, the thickness ofthe filter can change or the index of refraction can change. The indexof refraction can be changed by modifying the filter layer, such as byaltering its chemical composition, e.g., by modifying it to have anon-uniform doping concentration. As a result, each channel (orrow/column of channels) can have an optical filter layer that has adifferent doping concentration, thereby resulting in a different CWL foreach channel (or row/column of channels) without having a modifiedthickness. Rotating a one-dimensional array of micro-optic channels witha graduated optical filter allows the system to measure light atdifferent wavelengths for each photosensor. Scanning a two-dimensionalarray of micro optic channels where the graduated filter is changingalong the direction of the scan allows the passive optic imager systemto measure light at multiple wavelengths for each position in space, butuses multiple photodetectors in the photosensor to do so. Such opticalsystems using graduated filters require synchronization of thephotosensor sampling so that different wavelength measurements are takenfor the same photosensor with the same field-of-view. Imaging systemsthat differentiate between many different wavelengths are sometimesreferred to as hyperspectral imagers. A hyperspectral imager oftenrequires that light from the wavelengths of interest all be focused inapproximately the same plane. This can be achieved by using anachromatic, apochromatic, superachromatic, or similar lens that isdesigned to limit the effects of chromatic aberration.

Hyperspectral imagers collect information from multiple wavelength bandsacross the electromagnetic spectrum. The absolute or relativeintensities of the wavelength bands can provide information aboutchemical concentrations. For example, chlorophyll content of certaincrops can be estimated using only a few wavelength bands. Similartechniques can be used to find valuable minerals or identify toxins.Spectral information can also be used to assist in the classification ofpedestrians, automobiles, and other objects similarly encountered in anautomotive environment.

A graduated neutral-density filter has a transmission that variesspatially across the filter, but the transmission is largely independentof wavelength (e.g. just as transmissive to red light as to blue light)at any given location. In a scanning imaging system, a graduatedneutral-density filter can be used to image the same point in space withvarying degrees of attenuation, thereby enabling a composite measurementwith higher dynamic range than would achievable with a non-graduatedfilter. A better understanding of a micro-optic receiver layer withgraduated filter can be achieved with reference to FIGS. 3A and 3B.

FIGS. 3A and 3B are perspective views of a simplified diagram ofdifferent embodiments of micro-optic receiver layers with graduatedfilter layers, according to some embodiments of the present disclosure.Specifically, FIG. 3A is a perspective view of a simplified diagram of amicro-optic receiver layer 300 with a graduated filter layer 302, andFIG. 3B is a perspective view of a simplified diagram of a micro-opticreceiver layer 301 with a graduated filter layer 312. As illustrated inFIGS. 3A and 3B, micro-optic receiver layer 300 and 301 each includesfour micro-optic receiver channels 304, 306, 308 and 310 arranged in twodimensions as a 2×2 array. Although FIGS. 3A and 3B illustrateembodiments having only 2×2 arrays, one skilled in the art understandsthat such embodiments are not limiting and that other embodiments can beconfigured to have any number of micro-optic receiver channels. It is tobe appreciated that in these diagrams, the thicknesses of filter layers302 and 312 and the thicknesses of the surrounding layers, which are notdrawn to scale, should be interpreted as the thicknesses of layers ofrefractive material in an interference filter. As these thicknesseschange, the characteristics (e.g. passband CWL) of the interferencefilter change. These embodiments can be used in a hyperspectral passiveoptic imager system.

As shown in FIGS. 3A and 3B, graduated filter layer 302 has graduallyincreasing thickness in one dimension across multiple columns ofmicro-optic receiver channels, and graduated filter layer 312 has astep-wise-increasing thickness in one dimension that has a constantthickness for each micro-optic receiver channel. Micro-optic receiverchannels 304 and 308 have the same filter thickness and detect the samewavelength of light. Micro-optic receiver channels 306 and 310 have thesame filter thickness and detect the same wavelength of light.Micro-optic receiver channels 304 and 308 can have a different filterthickness than micro-optic receiver channels 306 and 310 and thus detecta different wavelength of light. During a first-time interval, themicro-optic receiver channels 304 and 308 measure the intensity of afirst wavelength of light for two pixels respectively. In someembodiments, the hyperspectral passive optic imager system moves orrotates the micro-optic receiver layer so that during a second-timeinterval, micro-optic receiver channels 306 and 310 measure theintensity of a second wavelength of light for the same two pixelsrespectively. In other embodiments, a hyperspectral passive optic imagersystem according to the disclosure can include a stationary micro-opticreceiver layer and scan a moving target.

II. Active Optical Imager Systems

As discussed herein, optical imager systems can also be configured asactive optical imager systems. Active optical imager systems can differfrom passive optical imager systems in that active optical imagersystems emit their own light into a field and detect the emitted lightafter it has reflected off surface(s) of an object in the field. In someembodiments, active optical imager systems can be utilized as LIDARdevices where emitted and received, reflected light can be correlated todetermine a distance to the object from which the emitted light wasreflected. A better understanding of an active optical imager system canbe ascertained with reference to FIG. 4.

FIG. 4 illustrates a block diagram of a LIDAR system 400 according tosome embodiments of the present disclosure. LIDAR system 400 can includea light ranging device 402 and a user interface 415. Light rangingdevice 402 can include a ranging system controller 404, a lighttransmission (Tx) module 406 and a light sensing (Rx) module 408.Ranging data can be generated by light ranging device 402 bytransmitting one or more light pulses 410 from the light transmissionmodule 406 to objects in a field of view surrounding light rangingdevice 402. Reflected portions 412 of the transmitted light are thendetected by light sensing module 408 after some delay time. Based on thedelay time, the distance to the reflecting surface can be determined.Other ranging methods can be employed as well, e.g. continuous wave,Doppler, and the like.

Tx module 406 includes an emitter array 414, which can be aone-dimensional or two-dimensional array of emitters, and a Tx opticalsystem 416, which when taken together with emitter array 414 can form alight emission system 438. Tx optical system 416 can include a bulktransmitter optic that is image-space telecentric. In some embodiments,Tx optical system 416 can further include one or more micro-opticstructures that increase the brightness of beams emanating from the bulktransmitter optic as discussed herein with respect to FIGS. 11-14 and/orfor beam shaping, beam steering or the like. Emitter array 414 or theindividual emitters can be laser sources. Tx module 406 can furtherinclude an optional processor 418 and memory 420, although in someembodiments these computing resources can be incorporated into rangingsystem controller 404. In some embodiments, a pulse coding technique canbe used, e.g., Barker codes and the like. In such cases, memory 420 canstore pulse-codes that indicate when light should be transmitted. Insome embodiments, the pulse-codes are stored as a sequence of integersstored in memory.

Light sensing module 408 can be substantially similar in construction tolight sensing module 106 discussed herein with respect to FIG. 1. Thus,details of processor 422, memory 424, sensor array 426, and Rx opticalsystem 428 (when taken together with sensor array 426 can form a lightdetection system 436) can be referenced herein with respect to FIG. 1,and only differences with respect to those components are discussedherein for brevity. For LIDAR system 400, each photosensor sensor (e.g.,a collection of SPADs) of sensor array 426 can correspond to aparticular emitter of emitter array 414, e.g., as a result of ageometrical configuration of light sensing module 408 and Tx module 406.For example, in some embodiments, emitter array 414 can be arrangedalong the focal plane of the bulk transmitter optic such that eachilluminating beam projected from the bulk transmitter optic into thefield ahead of the system is substantially the same size and geometry asthe field of view of a corresponding receiver channel at any distancefrom the system beyond an initial threshold distance.

In some embodiments, processor 418 can perform signal processing of theraw histograms from the individual photon detectors (or groups ofdetectors) in the array. As an example of signal processing, for eachphoton detector or grouping of photon detectors, memory 424 (e.g., SRAM)can accumulate counts of detected photons over successive time bins, andthese time bins taken together can be used to recreate a time series ofthe reflected light pulse (i.e., a count of photons vs. time). Thistime-series of aggregated photon counts is referred to herein as anintensity histogram (or just histogram). Processor 418 can implementmatched filters and peak detection processing to identify return signalsin time. In addition, Processor 418 can accomplish certain signalprocessing techniques (e.g., by processor 422), such as multi-profilematched filtering to help recover a photon time series that is lesssusceptible to pulse shape distortion that can occur due to SPADsaturation and quenching. In some embodiments, all or parts of suchfiltering can be performed by processor 458, which may be embodied in anFPGA.

In some embodiments, the photon time series output from processor 418are sent to ranging system controller 404 for further processing, e.g.,the data can be encoded by one or more encoders of ranging systemcontroller 404 and then sent as data packets to user interface 415.Ranging system controller 404 can be realized in multiple waysincluding, e.g., by using a programmable logic device such an FPGA, asan ASIC or part of an ASIC, using a processor 430 with memory 432, andsome combination of the above. Ranging system controller 404 cancooperate with a stationary base controller or operate independently ofthe base controller (via pre-programmed instructions) to control lightsensing module 408 by sending commands that include start and stop lightdetection and adjust photodetector parameters. Similarly, ranging systemcontroller 404 can control light transmission module 406 by sendingcommands, or relaying commands from the base controller, that includestart and stop light emission controls and controls that can adjustother light-emitter parameters (e.g., pulse codes). In some embodiments,ranging system controller 404 has one or more wired interfaces orconnectors for exchanging data with light sensing module 408 and withlight transmission module 406. In other embodiments, ranging systemcontroller 404 communicates with light sensing module 408 and lighttransmission module 406 over a wireless interconnect such as an opticalcommunication link.

Light ranging device 402 can be used in both stationary and a scanningarchitectures. Electric motor 434 is an optional component in LIDARsystem 400 that can be used to rotate system components, e.g., the Txmodule 406 and Rx module 408, as part of a scanning LIDAR architecture.The system controller 404 can control the electric motor 434 and canstart rotation, stop rotation and vary the rotation speed as needed toimplement a scanning LIDAR system. Exemplary stationary LIDAR devicesare discussed below with respect to FIGS. 5A and 5B, while exemplaryscanning LIDAR devices are discussed further herein with respect toFIGS. 6A, 6B, and 7.

LIDAR system 400 can interact with one or more instantiations of a userinterface 415. The different instantiations can vary and can include,but not be limited to, a computer system with a monitor, keyboard,mouse, CPU and memory; a touch-screen in an automobile or other vehicle;a handheld device with a touch-screen; or any other appropriate userinterface. User interface 415 can be local to the object upon whichLIDAR system 400 is mounted but can also be a remotely operated system.For example, commands and data to/from LIDAR system 400 can be routedthrough a cellular network (LTE, etc.), a personal area network(Bluetooth, Zigbee, etc.), a local area network (WiFi, IR, etc.), or awide area network such as the Internet.

User interface 415 of hardware and software can present the LIDAR datafrom the device to the user or to a vehicle control unit (not shown) butcan also allow a user to control LIDAR system 400 with one or morecommands. Example commands can include commands that activate ordeactivate the LIDAR system, specify photodetector exposure level, bias,sampling duration and other operational parameters (e.g., emitted pulsepatterns and signal processing), specify light emitters parameters suchas brightness. In addition, commands can allow the user to select themethod for displaying results. The user interface can display LIDARsystem results which can include, e.g., a single frame snapshot image, aconstantly updated video image, and/or a display of other lightmeasurements for some or all pixels. In some embodiments, user interface415 can track distances (proximity) of objects from the vehicle, andpotentially provide alerts to a driver or provide such trackinginformation for analytics of a driver's performance.

In some embodiments, for example where LIDAR system 400 is used forvehicle navigation, user interface 415 can be a part of a vehiclecontrol unit that receives output from, and otherwise communicates withlight ranging device 402 and/or user interface 415 through a network,such as one of the wired or wireless networks described above. One ormore parameters associated with control of a vehicle can be modified bythe vehicle control unit based on the received LIDAR data. For example,in a fully autonomous vehicle, LIDAR system 400 can provide a real time3D image of the environment surrounding the car to aid in navigation inconjunction with GPS and other data. In other cases, LIDAR system 400can be employed as part of an advanced driver-assistance system (ADAS)or as part of a safety system that, e.g., can provide 3D image data toany number of different systems, e.g., adaptive cruise control,automatic parking, driver drowsiness monitoring, blind spot monitoring,collision avoidance systems, etc. When user interface 415 is implementedas part of a vehicle control unit, alerts can be provided to a driver ortracking of a proximity of an object can be tracked.

A. Solid State Architecture

LIDAR systems, according to some embodiments of the present disclosure,can be configured as a solid state LIDAR system that has a stationaryarchitecture. Such LIDAR systems do not rotate, and thus do not need aseparate motor, e.g., electric motor 434 in FIG. 4, to rotate the sensorand transmitter modules. Example solid state LIDAR systems are shown inFIGS. 5A and 5B.

FIGS. 5A and 5B are simple illustrations of exemplary implementations ofsolid state LIDAR systems. Specifically, FIG. 5A illustrates animplementation 500 where solid state LIDAR systems 502 a-d areimplemented at the outer regions of a road vehicle 505, such as anautomobile, according to some embodiments of the present disclosure; andFIG. 5B illustrates an implementation 501 where solid state LIDARsystems 504 a-b are implemented on top of road vehicle 505, according tosome embodiments of the present disclosure. In each implementation, thenumber of LIDAR systems, the placement of the LIDAR systems, and thefields of view of each LIDAR system can be chosen to obtain a majorityof, if not the entirety of, a 360 degree field of view of theenvironment surrounding the vehicle. Automotive implementations for theLIDAR systems are chosen herein merely for the sake of illustration andthe sensors described herein may be employed in other types of vehicles,e.g., boats, aircraft, trains, etc., as well as in a variety of otherapplications where 3D depth images are useful, such as medical imaging,mobile phones, augmented reality, geodesy, geomatics, archaeology,geography, geology, geomorphology, seismology, forestry, atmosphericphysics, laser guidance, airborne laser swath mapping (ALSM), and laseraltimetry.

With reference to FIG. 5A, solid state LIDAR systems 502 a-d can bemounted at the outer regions of a vehicle, near the front and backfenders. LIDAR systems 502 a-d can each be positioned at a respectivecorner of vehicle 505 so that they are positioned near the outermostcorners of vehicle 505. That way, LIDAR systems 502 a-d can bettermeasure the distance of vehicle 505 from objects in the field at areas506 a-d. Each solid state LIDAR system can face a different direction(possibly with partially and/or non-overlapping fields of views betweenunits) so as to capture a composite field of view that is larger thaneach unit is capable of capturing on its own. Objects within the scenecan reflect portions of light pulses 510 that are emitted from LIDAR Txmodule 508. One or more reflected portions 512 of light pulses 510 thentravel back to LIDAR system 502 a and can be received by Rx module 509.Rx module 509 can be disposed in the same housing as Tx module 508.

Although FIG. 5A illustrates four solid state LIDAR systems mounted atthe four corners of a vehicle, embodiments are not limited to suchconfigurations. Other embodiments can have fewer or more solid stateLIDAR systems mounted on other regions of a vehicle. For instance, LIDARsystems can be mounted on a roof of a vehicle 505, as shown in FIG. 5B.In such embodiments, LIDAR systems can have a higher vantage point tobetter observe areas 506 a-d around vehicle 505.

B. Scanning Architecture

In some embodiments, LIDAR systems according to the present disclosurecan employ a scanning architecture in which the LIDAR system oscillatesbetween an angle that is less than 360 degrees. For instance, LIDARsystems 504 a-b in implementation 501 of FIG. 5B can each employ ascanning architecture to scan the entire scene in front of, and/orbehind, vehicle 505, e.g., in area 514 between field of view 506 a and506 b and in area 516 between field of view 506 c and 506 d. The outputbeam(s) of one or more light sources (not shown, but can be a variety ofdifferent suitable sources for emitting radiation including, but notlimited to lasers, in any wavelength spectrum suitable for LIDARsystems, such as in the infrared, near-infrared, ultraviolet, visible,e.g., green laser wavelength spectrum, and the like) located in thescanning LIDAR systems, can be outputted as pulses of light and scanned,e.g., rotated between an angle that is less than 360 degrees, toilluminate a scene around the vehicle. In some embodiments, thescanning, represented by rotation arrows 514 and 516, can be implementedby mechanical means, e.g., by mounting the light emitters to a rotatingcolumn or platform or through the use of other mechanical means, such asgalvanometers. Chip-based beam steering techniques can also be employed,e.g., by using microchips that employ one or more MEMS based reflectors,e.g., such as a digital micromirror (DMD) device, a digital lightprocessing (DLP) device, and the like. In some embodiments, the scanningcan be effectuated through non-mechanical means, e.g., by usingelectronic signals to steer one or more optical phased arrays.

Other embodiments can implement a scanning architecture that scansthrough the entire 360 degrees of the environment surrounding a vehicle.Such scanning LIDAR systems can repetitively rotate continuously through360 degrees in a clockwise or counter-clockwise direction, and thus mayutilize a separate motor, e.g., electric motor 434 in FIG. 4, to rotatethe sensor and transmitter modules. Exemplary rotating LIDAR systems areshown in FIGS. 6A and 6B.

FIG. 6A is a top-down view of a simplified diagram of an exemplaryscanning LIDAR system 600 implemented for a vehicle 605, such as a car,and capable of continuous 360 degree scanning, according to someembodiments of the present disclosure. The output beam(s) of one or morelight sources (such as infrared or near-infrared pulsed IR lasers, notshown) located in LIDAR system 600, can be scanned, e.g., rotated, toilluminate a continuous scene 620 around the vehicle. In someembodiments, the scanning, represented by rotation arrow 615, can beimplemented by any suitable mechanical means discussed herein withrespect to FIG. 5B, e.g., by mounting the light emitters to a rotatingcolumn or platform, or any other mechanical means, such as through theuse of galvanometers or chip-based steering techniques. Duringoperation, objects around vehicle 605 in any direction and within theview of LIDAR system 600 can reflect portions of light pulses 611 thatare emitted from a transmitting module 608 in LIDAR system 600. One ormore reflected portions 617 of light pulses 611 then travel back toLIDAR system 600 and can be detected by its sensing module 609. In someinstances, sensing module 609 can be disposed in the same housing astransmitting module 608.

Although FIG. 6A illustrates solid state LIDAR systems mounted on a roofof a vehicle 605, embodiments are not limited to such configurations.Other embodiments can have solid state LIDAR systems mounted on otherregions of a vehicle. For instance, LIDAR systems can be mounted at thecorners of a vehicle, as shown in FIG. 6B. FIG. 6B illustrates animplementation 601 where solid state LIDAR systems 604 a-d areimplemented at the outer regions of a road vehicle, such as a car,according to some embodiments of the present disclosure. In thisimplementation, each LIDAR system 604 a-d can be a spinning LIDAR systemthat can measure distances around the full 360 degrees. However, sinceat least some of those measurements will be measured with respect tovehicle 605, those measurements can be ignored. Thus, each LIDAR system605 a-d can only utilize a subset of the measurements from 360 degreescanning, e.g., only the angles covering regions 619 a-d that do notcapture vehicle 605 are utilized.

FIG. 7 is a simplified exemplary perspective view of a LIDAR system 700that employs a 360 scanning architecture, according to some embodimentsof the present disclosure. In some embodiments, LIDAR system 700 caninclude a light ranging device 701 that spins in a clockwise orcounter-clockwise direction to observe the surrounding field around avehicle. System 700 can include a stationary housing 702, an opticallytransparent window 704, and a stationary lid 706 for providingprotection for the internal components of LIDAR system 700. Window 704can extend fully around a periphery of stationary housing 702, which canbe configured to have a cylindrical shape. The internal components ofsystem 700 can include light ranging device 701, which can include arotating platform 708 and sensing and transmitting modules 710 mountedon rotating platform 708. In some embodiments, light ranging device 701is aligned with window 704 such that modules 710 are positioned to emitand receive light through window 704, and that emitted light is notemitted onto stationary housing 702 or stationary lid 706. For instance,in the aligned positioned, the horizontal center of light ranging device701 coincides with the horizontal center of window 704. Sensing andtransmitting modules 710 can be, for example, light sensing module 408and light transmission module 406, and can optionally include a heatsink (not shown) to cool the micro-optic layers. LIDAR system 700 canalso include a system controller 712 (e.g., controller 404) and electricmotor 714 (e.g., motor 434) that reside within stationary housing 702.Electric motor 714 rotates platform 708, thereby rotating sensing andtransmitting modules 710 in a spinning manner, e.g., continuouslythrough 360 degrees in a clockwise or counter-clockwise direction.System controller 712 can communicate with sensing and transmittingmodules 710 using an optical communication link 716. Opticalcommunication link 716 allows sensing and transmitting modules 710 tocommunicate with stationary system controller 712, which is mechanicallycoupled to stationary housing 702 and does not rotate with platform 708,through optical communication link 716 without mechanical wear and tear.In some embodiments, system controller 712 can control the motor and tostart and stop light detection operations of LIDAR system 700. Systemcontroller 712 can include two or more stacked planar circuit boardsarranged in a parallel relationship, which is discussed in more detailin commonly-owned and concurrently-filed patent application 16/209,867,entitled “Compact Lidar System”, which is herein incorporated byreference in its entirety for all purposes.

III. Operation of Active Imager Systems

FIG. 8 is an illustrative example of the light transmission anddetection operation for a light ranging system according to someembodiments. FIG. 8 shows a light ranging system 800 (e.g., solid stateor and/or scanning system) collecting three-dimensional distance data ofa volume or scene that surrounds the system. FIG. 8 is an idealizeddrawing to highlight relationships between emitters and sensors, andthus other components are not shown.

Light ranging system 800 includes a light emitter array 810 and a lightsensor array 820. The light emitter array 810 includes an array of lightemitters, e.g., an array of vertical-cavity surface-emitting lasers(VCSELs) and the like, such as emitter 812 and emitter 816. Light sensorarray 820 includes an array of photosensors, e.g., sensors 822 and 826.The photosensors can be pixelated light sensors that employ, for eachphotosensor, a set of discrete photodetectors such as single photonavalanche diodes (SPADs) and the like. However, various embodiments candeploy other types of photon sensors.

Each emitter can be slightly offset from its neighbor and can beconfigured to transmit light pulses into a different field of view fromits neighboring emitters, thereby illuminating a respective field ofview associated with only that emitter. For example, emitter 812 emitsan illuminating beam 814 (formed from one or more light pulses) into thecircular field of view 832 (the size of which is exaggerated for thesake of clarity). Likewise, emitter 816 emits an illuminating beam 818(also called an emitter channel) into the circular field of view 834.While not shown in FIG. 8 to avoid complication, each emitter emits acorresponding illuminating beam into its corresponding field of viewresulting in a 2D array of fields of view being illuminated (21 distinctfields of view in this example).

Each field of view that is illuminated by an emitter can be thought ofas a pixel or spot in the corresponding 3D image that is produced fromthe ranging data. Each emitter channel can be distinct to each emitterand be non-overlapping with other emitter channels, i.e., there is aone-to-one mapping between the set of emitters and the set ofnon-overlapping fields or view. Thus, in the example of FIG. 8, thesystem can sample 21 distinct points in the 3D space. A denser samplingof points can be achieved by having a denser array of emitters or byscanning angular position of the emitter beams over time such that oneemitter can sample several points in space. As described above, scanningcan be accomplished by rotating the entire emitter/sensor assembly.

Each sensor can be slightly offset from its neighbor and, like theemitters described above, each sensor can see a different field of viewof the scene in front of the sensor. Furthermore, each sensor's field ofview substantially coincides with, e.g., overlaps with and is the samesize as a respective emitter channel's field of view.

In FIG. 8, the distance between corresponding emitter-receiver channelsis exaggerated relative to the distance to objects in the field of view.In practice, the distance to the objects in the field of few is muchgreater than the distance between corresponding emitter-receiverchannels and thus the path of light from the emitter to the object isapproximately parallel to the path of the reflected light back from theobject to the sensor (i.e., it is almost “back reflected”). Accordingly,there is a range of distances in front of the system 800 over which thefields of view of individual sensors and emitters are overlapped.

Because the fields of view of the emitters are overlapped with thefields of view of their respective sensors, each receiver channelideally can detect the reflected illumination beam that originates fromits respective emitter channel with ideally no cross-talk, i.e., noreflected light from other illuminating beams is detected. Thus, eachphotosensor can correspond to a respective light source. For example,emitter 812 emits an illuminating beam 814 into the circular field ofview 832 and some of the illuminating beam reflects from the object 830.Ideally, a reflected beam 824 is detected by sensor 822 only. Thus,emitter 812 and sensor 822 share the same field of view, e.g., field ofview 832, and form an emitter-sensor pair. Likewise, emitter 816 andsensor 826 form an emitter-sensor pair, sharing field of view 834. Whilethe emitter-sensor pairs are shown in FIG. 8 as being in the samerelative locations in their respective array, any emitter can be pairedwith any sensor depending on the design of the optics used in thesystem.

During a ranging measurement, the reflected light from the differentfields of view distributed around the volume surrounding the LIDARsystem is collected by the various sensors and processed, resulting inrange information for any objects in each respective field of view. Asdescribed above, a time-of-flight technique can be used in which thelight emitters emit precisely timed pulses, and the reflections of thepulses are detected by the respective sensors after some elapsed time.The elapsed time between emission and detection and the known speed oflight is then used to compute the distance to the reflecting surface. Insome embodiments, additional information can be obtained by the sensorto determine other properties of the reflecting surface in addition tothe range. For example, the Doppler shift of a pulse can be measured bythe sensor and used to compute the relative velocity between the sensorand the reflecting surface. The pulse strength can be used to estimatethe target reflectivity, and the pulse shape can be used to determine ifthe target is a hard or diffuse material.

In some embodiments, the LIDAR system can be composed of a relativelylarge 2D array of emitter and receiver channels and operate as a solidstate LIDAR, i.e., it can obtain frames of range data without the needto scan the orientation of the emitters and/or sensors. In otherembodiments, the emitters and sensors can be scanned, e.g., rotatedabout an axis, to ensure that the fields of view of the sets of emittersand sensors sample a full 360 degree region (or some useful fraction ofthe 360 degree region) of the surrounding volume. The range datacollected from the scanning system, e.g., over some predefined timeperiod, can then be post-processed into one or more frames of data thatcan then be further processed into one or more depth images or 3D pointclouds. The depth images and/or 3D point clouds can be further processedinto map tiles for use in 3D mapping and navigation applications.

According to some embodiments, a light ranging system (also called acoded-pulse optical receiver system) can transmit multiple pulses oflight. In some embodiments, each coded-pulse has an embeddedpositive-valued pulse-code formed by the light intensity. The system candetermine the temporal position and/or amplitude of optical pulses inthe presence of background light by creating an intensity histogram ofdetected, reflected light at different time bins. For each time bin, thesystem adds a weighted value to the intensity histogram that depends onthe intensity of detected light. The weighted values can be positive ornegative and have varying magnitudes.

By selecting different combinations of positive-valued pulse-codes andapplying different weights, the system can detect positive-valued andnegative-valued codes suitable for standard digital signal processingalgorithms. This approach gives a high signal-to-noise ratio whilemaintaining a low uncertainty in the measured temporal position of thereflected light pulses.

FIG. 9 is a flowchart illustrating a method 900 of using coded pulses inan optical measurement system according to embodiments of the presentdisclosure. The optical measurement system may be a light rangingsystem. Method 900 can detect the temporal position of a reflected pulsefrom a target using multiple coded-pulses. In a real-timethree-dimensional application, method 900 can constantly detectdistances to objects in the surrounding environment. Method 900 may beimplemented by any of the optical measurement systems described herein.

At 910, a coded-pulse optical system (CPOS) performs an initialization.For example, the CPOS can respond to user interface commands forstarting, stopping, and changing parameters. The CPOS can initialize anoptical transmitter to indicate parameters, e.g., pulse-codes, lightpower level, and various time intervals (e.g., for a detection interval,an interval for pausing between detection intervals, and an overallmeasurement time interval). The CPOS can initialize a light sensingmodule to indicate parameters such as pulse-time-interval andlight-sampling-interval. The CPOS can also clear histogram values.

At 920, a pulse train is transmitted from a light source (e.g., a laser)as part of an optical measurement. The pulse train can be transmitted aspart of N pulse trains transmitted for the measurement. The N pulsetrains can reflect from an object, thereby allowing a rangingmeasurement to the object. Each of the N pulse trains can include one ormore pulses from the light source (e.g., VCSELs) and correspond to adifferent time interval that is triggered by a start signal.

In some embodiments, the CPOS can wait for a specified time to allow aprevious pulse train (coded-pulse transmission) to dissipate. The CPOScan then transmit a next pulse train of the N pulse trains of ameasurement, where the N pulse trains form a code. Once a measurement iscomplete, e.g., a last of the N pulse train has dissipated (e.g., aftera predetermined time expected for any reflections), the CPOS can thenstart the first/next coded-pulse transmission using the appropriatepulse-code. N can be an integer greater than one, e.g., 2, 3, 4, 5, orhigher.

At 930, optical detection can be started, e.g., in response to the startsignal that triggers the pulse train to be transmitted. Thus, the CPOScan start light detection at the same time that it started coded-pulsetransmission. As part of the optical detection, a pulse train can bedetected by a photosensor (e.g., corresponding to a pixel) of theoptical measurement system, thereby generating data values at aplurality of time points. In some embodiments, the photosensor is acollection of photodetectors (e.g., SPADs). The data values may be ofvarious forms, e.g., counts of a number of SPADs that triggered at atime point (e.g., within a time bin of a histogram). As other examples,the data values can be a digitized value from an ADC that follows ananalog photosensor (e.g., an APD). Both examples can correspond to anintensity. In total, N pulse trains can be detected. Further, theprocess can be performed separately for each photosensor of the opticalmeasurement device.

At 940, a weight is assigned to the data values at time points withinthe time interval corresponding to the pulse train, thereby obtainingweighted values. A weight can be assigned for each of the N pulsetrains. Some of such weights for different pulse trains can be the sameas other pulse trains. In some embodiments, at least two of the N pulsetrains are assigned different weights and have a different pulsepattern. Two pulse trains can have some similarity (e.g., portions ofpulses can overlap), but there is at least some times where one pulsetrain is ON and the other pulse train is OFF. Such different pulsepatterns can have a similar shape but have a different delay, e.g., {1,0, 1, 1, 0} has a similar shape of non-zero values to {0, 1, 0, 1, 1},but they are different pulse patterns due to an offset as may beachieved by a delay in the second signal relative to the first signal.

Accordingly, the CPOS can detect light and create a digitized intensityvalue for each light-sampling-interval. For eachlight-sampling-interval, the CPOS can apply a pulse-weight to thedigitized intensity value and add the result to the appropriate time-binof the intensity histogram.

At 950, the CPOS tests if it has sent the required number ofcoded-pulses. If the CPOS has sent the required number of coded-pulsesit continues at block 960, otherwise it loops back to block 920.

At 960, a histogram corresponding to the weighted values in a pluralityof time bins is determined. As described above, a counter of thehistogram at a particular time bin can be determined by accumulating theweighted values at time points within the particular time bin across aplurality of time intervals.

At 970, the histogram is used to detect a signal corresponding to the Npulse trains. For example, the CPOS can determine whether the histogramhas a sequence of values that match the match-code (filter). The CPOScan report whether the match-code was found and the amplitude of thematch. The match may allow detection of the desired signal relative tonoise or interference from other light sources.

As an example, a filter can include a set of values to be applied to awindow of time bins of a histogram. The filter can be slid over thehistogram to calculate a filtered histogram having counterscorresponding to different sliding positions of the profile filterrelative to the histogram. Each of the counters of the filteredhistogram can correspond to an overlap of the profile filter and thehistogram at a particular sliding position. A maximum value of thecounters of the filtered histogram can be identified, thereby allowingdetection, e.g., when the maximum value is above a threshold. Theparticular sliding position for the maximum value of the counters cancorrespond to the received time, which may be used for rangingmeasurements.

In some embodiments, the signal may be a reflected signal caused by theN pulse trains reflecting from an object, e.g., when the opticalmeasurement system is configured to perform ranging measurements. Inother embodiments, the signal may be a communication signal, e.g., whenthe light source is at one location and the photosensors are at adifferent location. Such a configuration can be used for communicationpurposes. For example, a microwave transmission tower can transmit datato a receiving tower. The transmitted data can include coded pulses,which may help to reduce errors in data reception as may be caused bynoise or interference from other sources. The receiving tower canidentify pulse trains and create a histogram by selecting an arbitrarytime between two pulse trains as a start time for a first time bin. Amatch filter can then be applied (e.g., by sliding over the histogram);and if a sufficient match is found, then that communication signal canbe detected. A sufficient match can be measured by the maximum valueobtained the filtered histogram. As a further embodiment, the system candetect an interference signal from another CPOS in a similar manner usedto detect the communication signal. If interference is measured, someimplementations can change the transmitted code, e.g., of theinterference code is similar to the code currently being used.

At 980, a distance to the object can be determined. For example, areceived time corresponding to the N pulse trains relative to the startsignal can be determined. A distance to the object can be determinedusing the received time. The received time may be offset from thetransmission times of the pulse trains, but such an offset can be takeninto account. Accordingly, the CPOS can report the time at which it wasdetected. The distance can corresponds to a round trip time between thereceived time and a start time of the start signal, and thus thedistance may be expressed in time.

The detected signal can be used for other purposes than ranging. Forexample, the quality of the detected signal can be used to measure thereflectivity of an object. For example, if the detected signal has astrong intensity, then the system can determine that the object has ahigh reflectivity. Implementations for communications and interferencemeasurements are discussed above. For detection of interference fromanother light source, the detected signal would be from another set ofpulse trains transmitted by the interfering light source.

As a generalization, embodiments can transmit N+1 unique codes with N+1unique weights to generate an N dimensional vector space histogram. Forexample, instead of a bin holding a signed number, the bin can hold a1-D vector (e.g., equivalent to a signed number), by transmitting atleast two unique codes: one positive and one negative. To store a 2-Dvector (e.g., in polar or Cartesian coordinates), the system cantransmit at least three unique codes, which could be weighted with threedifferent polar angles and sum to a single 2-D vector. An N-D vector(defined with N separate numbers all held within a single “bin”) wouldrequire N+1 different codes, each weighted at a different angle (inother worlds having a component to its weight that is orthogonal to allother weights) when doing the vector summation. By increasing thedimensionality, more advanced coding techniques like quadrature phasecoding or code division multiple access (CDMA) that are used in RFcommunications may be used. An N-dimensional matched filter can be usedin this context.

As a LIDAR system implements method 900 during its operation, the LIDARsystem can continuously measure distances to objects in the field.Accordingly, once the distance to an object is determined, method 900can loop back to block 920 to begin another series of emitting pulsetrains and detecting the emitted pulse trains to determine a histogramfor determining a distance to an object in the field. Distances may needto be constantly measured by method 900 because the LIDAR system mayneed to be constantly measuring distances to objects in the field, suchas when the LIDAR system is used for navigational purposes and the LIDARsystem is moving within the field.

In some embodiments, after determining the distance to the object atblock 980, method 900 can determine whether an exit command has beenreceived by CPOS at block 990. If an exit command has been received,then method 900 can stop measuring distances at block 999, otherwisemethod 900 can continue measuring distances to objects by looping backto block 920.

As mentioned above, method 900 can be used to reduce interference amongchannels. For example, method 900 can be repeated for a plurality ofchannels of light sources and photosensors as part of a plurality ofoptical measurements. The plurality of optical measurements can overlapin time, e.g., performed substantially simultaneously. Thus, eachchannel can perform a measurement at the same time. To reduceinterference, the codes can be different for at least some of thechannels. For example, the pulse patterns of the N pulse trains of atleast two channels of the plurality of channels can be different,thereby causing different histogram patterns for different channels. Inaddition or instead, the weights assigned to the N pulse trains of atleast two channels of the plurality of channels can be different,thereby causing different histogram patterns for different channels.

IV. Construction of Active Imager Systems

FIG. 10 is a simplified diagram illustrating a detailed view of anexemplary active optical imager system 1000 having a wide field-of-viewand capable of narrowband imaging, according to some embodiments of thepresent disclosure. Active optical imager system 1000 can employ solidstate or scanning architectures as aforementioned herein. In someembodiments, active optical imager system 1000 can include a lightdetection system 1001 and a light emission system 1002, which is unlikepassive optical imager systems. Light emission system 1002 providesactive illumination of at least a portion of a field in which system1000 is positioned with narrowband light rays 1004. Light detectionsystem 1001 detects the narrowband light emitted from the light emissionsystem 1002 after it has been reflected by objects in the field asreflected light rays 1006. Light detection system 1001 can besubstantially similar to light detection system 200 discussed hereinwith respect to FIG. 2. Thus, details of bulk receiver optic 1008, lightcone 1010, micro-optic receiver channel 1012 in micro-optic receiverlayer 1014, and photodetectors 1016 can be referenced herein withrespect to FIG. 2, and are not discussed herein for brevity.

In some embodiments, light emission system 1002 includes a bulktransmitter optic 1018 and a light emitting layer 1020 formed of a one-or two-dimensional array of light emitters 1022. Each light emitter 1022can be configured to generate discrete beams of narrowband light. Insome embodiments, light emitting layer 1020 is configured to selectivelyproject the discrete beams of light through bulk transmitter optic 1018according to an illumination pattern that matches, in size and geometryacross a range of distances from light emission system 1002, the fieldsof view of the receiver channels in micro-optic receiver channel array1014. Light emitters 1022 can be any suitable light emitting device,such as a vertical-cavity surface-emitting lasers (VCSELS) integrated onone or more monolithic chip, or any other type of laser diode. Lightemitters 1022 can produce cones of narrowband light 1024 that aredirected to bulk transmitter optic 1018, which can collimate cones oflight 1024 and then output the collimated light to distant targets inthe field as emitted light rays 1004. In some embodiments, bulktransmitter optic 1018 is image-space telecentric.

In additional and alternative embodiments, light rays 1004 from lightcones 1024 are focused on an intermediate plane in space by amicro-optic transmitter layer (not shown) before being directed todistant targets by the bulk transmitter optic 1018 to enhance thebrightness and intensity of light emitted from light emission system1002. In such embodiments, embodiments, light emission system 1002 andlight detection system 1001 are configured such that each micro-optictransmitter channel (not shown) is paired with a correspondingmicro-optic receiver channel 1012 and the centers of theirfields-of-view are aligned to be overlapping at a certain distance fromthe sensor or their chief rays are made parallel. In further additionaland alternative embodiments, the far-field beams of light emitted bylight emission system 1002 are of similar size and divergence angle tothe far-field fields-of-view of each micro-optic receiver channel 1012.Details of light emission systems 1002 having the micro-optictransmitter layer for enhancing brightness and intensity of outputtedlight will be discussed in detail below.

As is evident from the illustration of parallel light rays 1004 and 1006in FIG. 10, each micro-optic receiver channel 1012 has a non-overlappingfield of view beyond a threshold distance. As shown in FIG. 10, eachmicro-optic receiver channel 1012 includes an aperture from theplurality of apertures, a lens from the plurality of lenses, and aphotodetector from the plurality of photodetectors, where the apertureof each channel defines a discrete field of view for the pixel in thechannel that is non-overlapping beyond a threshold distance within thefields of view of the other micro-optic receiver channels. That way,each micro-optic receiver channel receives reflected light correspondingto a discrete position in the field that is not measured by any othermicro-optic receiver channel in micro-optic receiver channel layer 1014.

A. Enhancing Brightness and Intensity of Transmitters in Active ImagerSystems

Embodiments of the present disclosure pertain to a LIDAR sensor thatcan, among other uses, be used for obstacle detection and avoidance inautonomous vehicles. Some specific embodiments pertain to LIDAR sensorsthat include design features that enable the sensors to be manufacturedcheaply enough and with sufficient reliability and to have a smallenough footprint to be adopted for use in mass-market automobiles,trucks and other vehicles. For example, some embodiments include a setof vertical-cavity surface-emitting lasers (VCSELs) as illuminationsources that emit radiation into a field and include arrays ofsingle-photon avalanche diode (SPAD) detectors as a set of photosensors(detectors) that detect radiation reflected back from a surface in thefield. Using VCSELs as the emitters and SPADs as the detectors enablesmultiple measurements to be taken at the same time (i.e., the VCSELemitters can be fired simultaneously) and also enables the set ofemitters and the set of photosensors to each be fabricated usingstandard CMOS processes on a single chip, greatly simplifying themanufacturing and assembly process.

Using VCSELs and SPADs in certain embodiments presents challenges,however, that various embodiments of the present disclosure overcome.For example, VCSELs are much less powerful than typical lasers used inexisting LIDAR architectures and SPADs are much less efficient than thetypical detectors used in the existing LIDAR architectures. To addressthese challenges, as well as challenges presented by firing multipleemitters simultaneously, certain embodiments of the disclosure includevarious optical components (e.g., lenses, filters, and an aperturelayer), which may work in concert with multiple arrays of SPADs, eacharray corresponding to a different pixel (e.g., position in the field),as described herein. For example, as discussed herein with respect toFIG. 2, a light detection system 200 can include a micro-optic receiverlayer 204 for enhancing the light detected by photosensors 216, e.g.,SPADs.

Because VCSELs are less powerful than typical lasers in existing LIDARarchitectures, in some embodiments, light emission system 1002 can beconfigured to improve the ability of imager system 1000 to perform lightranging functionality. That is, the quality of light emitted by lightemission system 1002 can be enhanced to improve light ranging accuracyand efficiency. The quality of transmitted light for light ranging andimaging purposes can be defined in terms of brightness and intensity.The brightness and intensity of light rays 1004 emitted from bulktransmitter optic 1018 can be enhanced by modifying and/or implementingone or more optic transmitter layers, as will be discussed furtherherein.

Brightness of a transmitting light can be defined by the optical power(in watts) per solid angle. Thus, light sources that output light withtight collimation, i.e., low divergence, produce light that are high inbrightness. Conversely, light sources that output light with highdivergence produce light that are low in brightness. Intensity of lightcan be defined by the optical power per area, meaning light emitted witha certain power will have higher intensity if it tightly compacted in asmall area. Accordingly, light sources that output light in a tightlycompacted ray will have higher intensity than light sources that outputlight in a less compacted ray, even if both light sources output lightthat has low divergence. As will be appreciated herein, transmittercomponents for LIDAR systems in embodiments of the present disclosurecan be configured with micro-optical components that enable thetransmitter to output light that has enhanced brightness and intensityas compared to a similar transmitter without the micro-opticalcomponents.

FIG. 11 is a simplified cross-sectional view diagram of a firstexemplary enhanced light emission system 1100, according to someembodiments of the present disclosure. Light emission system 1100 caninclude a light emitter array 1102 having light emitters 1104 that forexample may comprise without limitation any of LEDs, laser diodes,VCSELs, or the like for emitting light 1113. A VCSEL is a type ofsemiconductor laser diode with laser beam emission perpendicular fromthe top surface. Note that the linear array shown in FIG. 11 can be anygeometric form of emitter array, including and without limitationcircular, rectangular, linear, or any other geometric shape.

Enhanced light emission system 1100 can include a micro-optictransmitter channel array 1106 separated from light emitter array 1102by an open space 1118. Each micro-optic transmitter channel 1108 ispaired with a corresponding receiver channel (e.g., receiver channel1012 in FIG. 10) and the centers of their fields-of-view are aligned tobe overlapping at a certain distance from the optical imager system.Micro-optic transmitter channel array 1106 can be formed of a substrate1119 sandwiched between a first optical surface 1120 positioned on aside facing light emitter array 1102 and a second optical surface 1121positioned on an opposite side facing away from light emitter array1102. Both first and second optical surfaces 1120 and 1121 can each beconfigured as an array of convex, micro-optic lenses where each convexlens of first optical surface 1120 is configured to be optically alignedwith a respective convex lenses of second optical surface 1120 so thatlight transmitting through first optical surface 1120 can subsequentlybe transmitted through second optical surface 1121. The correspondingconvex lenses from first and second optical surfaces 1120 and 1121 canface away from one another as shown in FIG. 11. In certain embodiments,convex lenses of first optical surface 1120 have a first optical powerand convex lenses of second optical surface 1121 have a second opticalpower different from the first optical power. For instance, the secondoptical power can be greater than the first optical power such that thefocal length of the second optical power is shorter than the focallength of the first optical power. Substrate 1119 can be formed of anysuitable material that is transmissive in the wavelength range of thelight emitters 1104 such silicon, silicon dioxide, borosilicate glass,polymer, and the like. First and second optical surfaces 1120 and 1121can be formed of a transparent polymer that is imprinted on respectiveopposite surfaces of substrate 1119.

In some embodiments, micro-optic transmitter channel array 1106 can beformed of a monolithic array of micro-optic transmitter channels 1108.Each micro-optic transmitter channel 1108 can include a first convexlens from first optical surface 1120, a corresponding second convex lensfrom second optical surface 1121, and a corresponding portion ofsubstrate 1119 positioned between the two convex lenses. Eachmicro-optic transmitter channel 1108 can correspond with a respectivelight emitter 1104 so that light outputted from the light emitter 1104first passes through the first convex lens, through the correspondingregion of substrate 1119, and then through the second convex lens duringoperation.

Once light emits out of the second convex lens of second optical surface1121, the light forms a miniature spot image 1110 that is a real imageof the corresponding light emitter 1104 but a reduced-size of thecorresponding light emitter 1104. In some embodiments, miniature spotimages 1110 are positioned between micro-optic transmitter channel array1106 and bulk transmitter optic 1114. For instance, miniature spotimages 1110 can be formed within respective apertures of an aperturelayer 1109. Each aperture can be a pin hole in a reflective or opaquelayer in which emitted light focuses to form miniature spot images 1110.From there, continuing away from both the light emitter and micro opticchannel, the light forms a light cone 1112 reaching out towards bulktransmitter optic 1114.

According to some embodiments of the present disclosure, the degree ofdivergence of emitted light 1113 can be smaller than the degree ofdivergence of light cone 1112. This discrepancy in divergence can becreated by a micro-optic transmitter channel 1108, specifically by theoptical power of second optical surface 1121. Because the divergence oflight out of micro-optic transmitter channel 1108 is larger than thedivergence of emitted light 1113 from light emitters 1104, miniaturespot image 1110 can be a real image of light emitter 1104 but amultitude smaller than the size of light emitter 1104 and with the samenumber of photons as emitted light 1113. The resulting light cone 1112formed after the real spot images are formed then gets projected intothe field as discrete beams of light for each light emitter 1104 afterpassing through bulk transmitter optic 1114. The resulting light raysemanating out of light emission system 1100 are highly collimated beamsof light that have a small cross-sectional area (smaller than thesurface area of light emitter 1104), thereby resulting in a lightemission system 1100 that can output light having enhanced brightnessand intensity.

Note that bulk transmitter optic 1114 can include either a single lensor a cluster of lenses where two or more lenses function together toform bulk transmitter optic 1114. The use of multiple lenses within thebulk transmitter optic 1114 could increase the numerical aperture,reduce the RMS spot size, flatten the image plane, improve thetelocentricity, or otherwise improve the performance of bulk transmitteroptic 1114. Note also that for some embodiments, light cones 1112 mayoverlap forming cone overlap region 1116.

To better understand the operation and effectiveness of micro-optictransmitter channel array 1106, a more detailed explanation of theoperation of light emission system 1100 is discussed. For enhanced lightemission systems 1100 utilizing a light emitter array formed of VCSELemitters, an exemplary initial radius for an emitter might be 12.5 umwith light admitted in a 10° half angle cone. Such emitters wouldtypically output 50 uW per square micron of active area. A diverginglight cone from each emitter 1104 is accepted into a micro-optictransmitter channel 1108, and then a converging light cone is output bythat same micro optic channel to produce a converging light cone with ahalf angle of for example 20°. Thus for some embodiments, the cone angleproduced by an emitter 1104 is smaller than the cone angle produced by acorresponding micro-optic transmitter channel 1108. The converging lightcone emanated by micro-optic transmitter channel 1108 then produces aminiature spot image 1110 of the emitter. For the embodiment accordingto FIG. 11, miniature spot image 1110 is a real image and has a sizethat is smaller than the size of a corresponding light emitter 1104.Note that all rays from a given emitter may not all be focused into anarbitrarily small spot. The miniature spot image size is typicallycontrolled by an “optical invariant”:Θ_s*r_s>=Θ_e*r_ewhere Θ_s is the marginal ray half angle of the focused spot, r_s is theradius of the focused spot, Θ_e is the marginal ray half angle of theoriginal emitter, and r_e is the radius of the original emitter. So, inthis example, the smallest miniature spot image radius that could beformed (while still capturing all the rays from the emitter) is:10/20*12.5 um=6.25 um

Note that this smaller spot will have one fourth the area of theoriginal emitter, and thus has a power density of 200 uW per squaremicron of spot area. Each micro-optic transmitter channel 1108 typicallyhas one or more optical surfaces, having characteristics that may forexample and without limitation include a focal length of 50 um, and alens diameter of 80 um. For some embodiments, the distance between lightemitter 1104 and a corresponding micro-optic transmitter channel 1108may be for example and without limitation 150 um. Open space 1118between emitter array 1102 and micro-optic transmitter channel array1106 as shown in FIG. 11 may be, for example and without limitation anair gap such as that produced by methods typically used to manufactureMEMS devices. The distance between emitter array 1102 and micro-optictransmitter channel array 1106 for example may be 150 um.

Bulk transmitter optic 1114 is positioned in front of the micro-opticand emitting layers such that the focal plane of the bulk imaging opticcoincides with miniaturized spot images 1110. Bulk transmitter optic1114 accepts divergent light cone(s) 1112 and outputs a collimated beam.Its numeric aperture can be at least large enough to capture the fullrange of angles in the divergent ray cone(s), so for example and withoutlimitation the Numerical Aperture (NA)=0.34 in this example. Also, bulktransmitter optic 1114 can be image-space telecentric, since lightcone(s) 1112 exiting the micro-optic layer may all be parallel (ratherthan having their center axes aimed towards the center of the bulkoptic). In one embodiment, light can exit bulk transmitter optic 1114approximately collimated. Note that the quality of beam collimationrelates to the size of the “emitting object” (miniature spot images1110) at the focal plane. Since this “emitting object” size has beenreduced by using a micro-optic stack, a better collimation angle isobtained than if the emitter object was simply imaged directly.

Although FIG. 11 shows an enhanced light emission system having amicro-optic channel array formed of a substrate sandwiched between firstand second optical surfaces, and positioned a distance away from a lightemitter array by an open space to improve the brightness and intensityof light outputted by the light emission system, embodiments are notlimited to such configurations. Rather, other embodiments may notnecessarily implement an open space or two optical surfaces, asdiscussed further herein with respect to FIG. 12.

FIG. 12 is a simplified cross-sectional view diagram of a secondexemplary enhanced light emission system 1200, according to someembodiments of the present disclosure. Similar to first exemplaryenhanced light emission system 1100, second exemplary enhanced lightemission system 1200 can include bulk imaging optic 1214 and lightemitter array 1202. However, unlike first exemplary light emissionsystem 1100, second exemplary light emission system 1200 can include amicro-optic transmitter channel array 1206 that is positioned directlyupon an emission surface of light emitter array 1202 instead of beingseparated by an open space/air gap, as shown in FIG. 12.

In such embodiments, micro-optic transmitter channel array 1206 can beformed of a substrate 1219 and an optical surface 1220. Optical surface1220 can be positioned on a first surface 1230 of substrate 1219. Secondsurface 1231 of substrate 1219 can be located opposite of first surface1230 and positioned against light emitter array 1202 so that lightemitted from emitters 1204 can first pass through substrate 1219 beforepassing through optical surface 1220. Optical surface 1220 can beconfigured as an array of convex lenses where each convex lens ofoptical surface 1220 is configured to be optically aligned with arespective light emitter 1204 so that light outputted by the respectivelight emitter 1204 can transmit through the respective convex lens ofoptical surface 1220. Convex lenses from optical surface 1220 can faceaway from their respective light emitters 1204 as shown in FIG. 12 sothat their focal points are positioned further from light emitter 1204.In certain embodiments, convex lenses of optical surface 1220 have anoptical power suitable for converging the emitted light into realminiature spot images 1210 that are real images of corresponding lightemitters 1204 but reduced-size images of the corresponding lightemitters 1204 like the convex lenses of second optical surface 1121 inFIG. 11. Optical surface 1120 enables the emitted light to diverge intolight cones 1212 before projecting through bulk imaging optic 1214.Substrate 1219 and optical surface 1220 can be formed of similarmaterials as substrate 1119 and optical surfaces 1120 and 1121 discussedherein with respect to FIG. 11. In some embodiments, light cones 1212may overlap forming cone overlap region 1216.

Embodiments herein can also implement micro-optic channel arrays that donot include convex lenses and that do not generate real images of thelight emitters. Rather, some embodiments may implement concave surfacesto generate virtual images of the light emitters, as discussed furtherherein with respect to FIG. 13.

FIG. 13 is a simplified cross-sectional view diagram of a thirdexemplary enhanced light emission system 1300, according to someembodiments of the present disclosure. Similar to first and secondexemplary enhanced light emission systems 1100 and 1200, third exemplaryenhanced light emission system 1300 can include bulk imaging optic 1314and light emitter array 1302. However, unlike first and second exemplarylight emission systems 1100 and 1200, third exemplary light emissionsystem 1300 can include a micro-optic transmitter channel array 1306that includes an array of concave surfaces instead of an array of convexlenses, as shown in FIG. 13.

In such embodiments, micro-optic transmitter channel array 1306 can beformed of a substrate 1319 and an optical surface 1320. Optical surface1320 can be a first surface 1330 of substrate 1319 positioned towardbulk imaging optic 1314 and away from light emitters 1304. Secondsurface 1331 of substrate 1319 can be located opposite of first surface1330 and positioned against light emitter array 1302 so that lightemitted from emitters 1304 can first pass through substrate 1319 beforepassing through optical surface 1320. Optical surface 1320 can each beconfigured as an array of concave surfaces where each concave surface ofoptical surface 1320 is configured to be optically aligned with arespective light emitter 1304 so that light outputted by the respectivelight emitter 1304 can transmit through the respective concave surfaceof optical surface 1320. In certain embodiments, the concave surfaces ofoptical surface 1320 have an optical power suitable for forming virtualminiature spot images 1310 that are virtual images of correspondinglight emitters 1304 but reduced-size images of the corresponding lightemitters 1304, and further enable the emitted light to diverge intolight cones 1312 before projecting through bulk imaging optic 1314. Insome embodiments, virtual miniature spot images 1310 are formed withinsubstrate 1319 as shown in FIG. 13. In some embodiments, light cones1312 may overlap forming cone overlap region 1316. Substrate 1319 can beformed of similar materials as substrate 1119 discussed herein withrespect to FIG. 11.

Note that the lens configurations for the micro-optic channels forembodiments described in each of FIGS. 11, 12 and 13 differs withrespect to how many surfaces have optical power and the shapes of thosesurfaces. The first embodiment shown in FIG. 11 benefits from theability to use two optical power surfaces on opposite sides of asubstrate, which could allow each surface to be shallower, sphericalrather than aspherical, or otherwise more easily manufactured. Thisembodiment includes a spacer structure (not shown) to maintain an offsetbetween the micro-optic channel array 1106 and the light emitter array1102. An example of such a spacer structure would be a silicon waferwith channels formed via deep reactive ion etching. The secondembodiment shown in FIG. 12 benefits from having only one optical powersurface on a substrate that is attached to the light emitter array. Thistype of configuration simplifies fabrication while also achievingenhanced brightness and intensity. The third embodiment shown in FIG. 13shares the benefits of the embodiment shown in FIG. 12 but has a singleoptical surface that is formed of concave surfaces rather than convexlenses; concave features can often be easier to fabricate at themicro-scale.

In some embodiments, bulk imaging optics for light emission systems caninclude one or more aperture stops to reduce stray light emitted by thesystem. For instance, FIG. 14 is a simplified cross-sectional viewdiagram of an exemplary enhanced light emission system 1400 configuredwith bulk optics that have aperture stops, according to some embodimentsof the present disclosure. FIG. 14 is substantially similar to FIG. 1with the addition of aperture stop variants 1403, 1405, and 1406 forbulk transmitter optic 1414. Aperture stop(s) shown in FIG. 14 can beused with any of FIGS. 11 through 13. In FIG. 14, aperture stops 1403,1405, and 1407, can have circular or oval openings for light to passthrough, although any opening shape may be utilized without deviatingfrom the spirit and scope of the present disclosure.

In some embodiments, aperture stop 1403 can be located on a side of bulktransmitter optic 1414 facing away from light emitter array 1402 andmicro-optic transmitter channel array 1406. In some additional andalternative embodiments, aperture stop 1405 can be located on a side ofbulk transmitter optic 1414 facing toward light emitter array 1402 andmicro-optic transmitter channel array 1406. In yet some additional andalternative embodiments where bulk receiver optic 114 includes aplurality of lenses working together, aperture stop 1407 can be formedof one or more aperture stops placed within the plurality of lenses thatform bulk transmitter optic 1414.

The various configurations and locations of aperture stops 1403, 1405,and 1407 can dictate the way each aperture stop functions in the lightemitting system. For example, if all the light cones 1412 are compressedto be substantially overlapping near the location of aperture stop 1407,then the size of the aperture stop 1407 would be able control both theinitial diameter of the emitted collimated beams as well as reject themarginal rays emitted by light emitters 1404. Rejecting certain rayangles could effectively narrow the spectrum of light emitted out of thebulk optic, since the wavelength of light emitted by many types oflasers varies with angle. Alternatively, perhaps this best location forthe aperture stop would occur at 1402 or 1403, depending upon the designof the bulk transmitter optic 1414. Multiple aperture stops may be usedsimultaneously—e.g. 1402, 1403, and 1404 all in one bulk transmitteroptic 1414—to reduce stray light emitted by light emitting system 1400.

B. Optical Corrections for Astigmatism

As mentioned herein with respect to FIG. 7, light detection systems andlight emission systems can be enclosed within the same protectivestructure, e.g., stationary housing 702, optically transparent window704, and stationary lid 706 in FIG. 7. Light emitted from the lightemission system, in some embodiments, exits out of transparent window704, and light detected by light detection system may first enter intotransparent window 704. The curvature of transparent window 704 caninduce some optical aberrations, such as astigmatism. Because thetransparent window can have a cylindrical structure and bewell-controlled, it can be corrected with one or more additional opticalstructures. In some embodiments, light emission and/or detection systemscan be configured with corrective optical structures to compensate forthe astigmatism caused by the transparent window, as discussed furtherherein.

FIGS. 15A-15C are cross-sectional views of simplified diagrams ofexemplary active imager systems having different implementations ofcorrective optical structures for astigmatism, according to someembodiments of the present disclosure. Specifically, FIG. 15A is asimplified cross-sectional view diagram of an active imager system 1500having a corrective optical structure as part of the bulk imaging optic,FIG. 15B is a simplified cross-sectional view diagram of an activeimager system 1501 having a corrective optical structure as part of themicro-optic receiver channel array, and FIG. 15C is a simplifiedcross-sectional view diagram of an active imager system 1502 having acorrective optical structure as part of the micro-optic transmitterchannel array. Active imager systems 1500, 1501, and 1502 each include alight detection system 1504 and a light emission system 1506. Componentsof active imager systems 1500, 1501, and 1502 are substantially similarto active optical imager system 1000 in FIG. 10 with the addition of thecorrective optical structures. Thus, the components that are shared withactive optical imager system 1000 are not discussed for brevity.

As shown in FIG. 15A, active imager system 1500 can be housed within anenclosure containing a transparent window 1508. Transparent window 1508is at least transparent to the wavelength of light at which emitters1510 operate. The curved shape of transparent window 1508 can induce anoptical aberration, such as an astigmatism, in light rays 1511 emittedfrom light emission system 1506 when light rays 1511 exit the enclosurethrough transparent window 1508. Light rays 1512 then enter back intothe enclosure through transparent window 1508 after reflecting off of anobject in the field, which can induce an additional optical aberrationto the received light rays. To correct for these optical aberrations,light detection system 1504 can include corrective bulk imaging optic1514 specifically designed to compensate for the expected astigmatisminduced by transparent window 1508. For example, corrective bulk imagingoptic 1514 can include a corrective lens 1516 in addition to bulkreceiver optic 1518. Corrective lens 1516 can be any suitable lenscapable of negating the astigmatism caused by transparent window 1508,such as a cylindrical lens. Corrective lens 1516 can be positionedbetween transparent window 1508 and bulk receiver optic 1518 in someembodiments, or between bulk receiver optic 1518 and micro-opticalreceiver channel array 1505 in some other embodiments. Similarly, acorrective bulk optic could be included in the bulk transmitter optic ofthe light emission system 1506.

Instead of incorporating the corrective optics into the bulk imagingoptics, the corrective optics can be implemented into a micro-opticalreceiver channel array in some embodiments. For instance, with referenceto FIG. 15B, light detection system 1504 can include a corrective lensarray 1520 in front of apertures 1522, e.g., on the opposite side ofapertures 1522 from where photosensors 1526 are positioned. That way,light cones 1524 can propagate through respective corrective lenses tocompensate for astigmatism caused by transparent window 1508 beforeprojecting on photosensors 1526. In some embodiments, corrective lensarray 1520 is formed of an array of cylindrical lenses that can negatethe astigmatism caused by transparent window 1508. Each corrective lensof corrective lens array 1520 can be positioned in alignment with arespective aperture 1522 so that corrective lens array 1520 can negatethe astigmatism caused by transparent window 1508 for light received byeach photosensor 1526.

Although FIGS. 15A and 15B illustrate ways in which a light detectionsystem portion of a LIDAR system can be modified to correct forastigmatism caused by transparent window 1508, embodiments are notlimited to such configurations and corrective optics can be implementedin light emission systems as well. For example, with reference to FIG.15C, active imager system 1502 can include a corrective lens array 1528in front of aperture layer 1530, e.g., on the opposite side of aperturelayer 1530 from where light emitters 1510 are positioned. That way,light emitted from light emitters 1510 can propagate through respectivecorrective lenses 1528 before emitting to bulk transmitter optics 1534.In this case, respective corrective lenses 1528 can induce a correctivedegree of astigmatism in the emitted light in anticipation of, and tocompensate for, the astigmatism caused by transparent window 1508 aslight is emitted out of light emission system 1506. In some embodiments,corrective lens array 1528 is formed of an array of biconical lensesthat can induce an equal but opposite degree of astigmatism caused bytransparent window 1508. Thus, the amount of astigmatism induced bycorrective lens layer 1528 can be offset by the degree of astigmatismcaused by transparent window 1508, thereby effectively achieving littleto no net astigmatism during operation of active imager system 1502.Each corrective lens of corrective lens array 1528 can be positioned inalignment with a respective aperture 1532 so that corrective lens array1528 can induce a corrective degree of astigmatism to negate theastigmatism caused by transparent window 1508 for light received by eachphotosensor 1526. In some embodiments, corrective lens array 1528 maynot be needed. Instead, optical surface 1536 can be an array ofbiconical lenses instead of an array of cylindrical lenses. Thebiconical structure of the lenses can induce an amount of astigmatism tooffset the degree of astigmatism caused by transparent window 1508. Inthese embodiments, corrective lens array 1528 may not be implemented inlight emission system 1506. Furthermore, in some embodiments, instead of(or in conjunction with) a corrective micro-optic lens array, acorrective bulk cylindrical lens can be implemented with bulk receiveroptic 1534 (similar to the embodiment shown in FIG. 15A for lightdetection system 1504). Thus, light emission system 1506 can include acorrective bulk imaging optic in front of its bulk receiver optic 1534to negate the astigmatism caused by transparent window 1508.

V. Mitigating Receiver Channel Cross-Talk

As can be appreciated by disclosures herein, channels in the micro-opticreceiver and are positioned very close to one another, often timeswithin microns of one another. This small spacing between each channelcan invite the opportunity for problems to arise. For instance, lightpropagating through bulk imaging optic can occasionally cause straylight to bleed into neighboring channels, thereby resulting ininaccurate readings of reflected light for each pixel in the field.Ideally, no stray light should be received by any channel, as shown inFIG. 16A.

FIG. 16A is a simplified cross-sectional view diagram of part of a lightdetection system 1600 where there is no cross-talk between channels.During operation, perpendicular light rays 1602 and chief ray 1604 enterthe bulk imaging optic 1606 and produce light cone 1608. Light rays 1602and 1604 enter an aperture of aperture layer 1610 and enter collimatinglens 1611. Collimating lens 1611 accepts a limited range of incidentlight angles. For example, collimating lens 1611 can accept light raysat incident angles between +25 to −25 degrees relative to theperpendicular. FIG. 16A shows light cone 1608 with incident anglesbetween +25 to −25 degrees. The chief ray 1604 is the light ray thatpasses through the center of the aperture. In this example, the chiefray 1604 has an incident angle of 0 degrees on the collimating lens1611.

FIG. 16B is a simplified cross-sectional view diagram of part of a lightdetection system 1601 where there is cross-talk between channels. Inthis case, during operation, oblique light rays 1612 and chief ray 1614enter bulk receiver optic 1616 and later enter collimating lens 1621. Inthis example, collimating lens 1621 belongs to a micro-optic channelthat corresponds to a photosensor further from the center of the image.In this example, chief ray 1614 has an incident angle of −12 degrees andthe cone of focused light has incident angles between +12 degrees to −35degrees. Collimating lens 1621 rejects some of the light rays because itonly accepts light with incident angles between +25 to −25 degrees.Additionally, the rays that are outside of the collimating lensacceptance cone can travel to other optical surfaces and become straylight. Thus, a non-telecentric bulk imaging optic will deliversignificantly fewer signal photons to the photodetector, whilepotentially polluting other channels with errant light rays 1622. Atelecentric bulk imaging optic, on the other hand, will produce lightcones with incident angles approximately between +25 to −25 degrees andchief rays with incident angles on the collimating lens of approximately0 degrees, regardless of the angle of the oblique rays 1612 and chiefray 1614. A telecentric bulk imaging optic has similar benefits for thetransmitter when the lasers are telecentric (their chief rays are allparallel) as is the case for VCSELS or a side emitter diode laser bar.

In some embodiments, the light detection system of a light sensingmodule uses an input image-space telecentric bulk imaging optic. In someother embodiments, for example where cost or increased field of view ismore important than performance, the light detection system may use amore standard input bulk imaging optic such as a bi-convex lens. For anygiven input field into an image-space telecentric lens, the resultingchief rays are parallel to the optical axis, and the image-side raycones all span approximately the same set of angles. This allowsmicro-optic channels far from the optical axis in the light detectionsystem to achieve similar performance to the on-axis micro-opticchannel. The light detection system does not need perfect image spacetelecentricity for this to work, but the closer to perfecttelecentricity the better. For a micro-optic receiver optical layer lensthat can only accept +/−25 degree light, the preference is that theinput bulk imaging optic produce image-side rays that are no greaterthan 25 degrees in angle for every point on the focal plane.

In certain embodiments, specific light detection systems having widefield of view and narrowband imaging can have an input image-spacetelecentric bulk imaging optic with a numerical aperture (NA) equal to0.34 and focal length of 20 mm. Similarly, some other embodiments couldhave a 1 nm wide bandpass filter, thereby enabling it to detect light ofa very specific wavelength. The light detection system is capable ofsupporting FOVs greater than 30 degrees.

According to some embodiments of the present disclosure, the design ofeach channel of the micro-optic receiver channel array can bespecifically configured to have features that minimize the intrusion ofstray light onto a respective photodetector, thereby reducing oreliminating any detrimental effects caused by the occurrence of straylight. FIG. 17 is a simplified cross-sectional diagram of an exemplarymicro-optic receiver channel structure 1700, also called a micro-opticreceiver channel in discussions herein. Receiver channel 1700 can berepresentative of micro-optic receiver channels 232 and 1032, amongothers, shown in FIGS. 2 and 10, respectively, and serves to accept aninput cone of light containing a wide range of wavelengths, filters outall but a narrow band of those wavelengths centered at the operatingwavelength, and allows photosensor 1771 to detect only or substantiallyonly photons within the aforementioned narrow band of wavelengths.According to some embodiments of the present disclosure, micro-opticreceiver channel structures, such as receiver channel 1700, can includethe following layers:

-   -   An input aperture layer 1740 including an optically transparent        aperture 1744 and optically non-transparent stop region 1746        configured to define a narrow field of view when placed at the        focal plane of an imaging optic such as bulk receiver optic 202        or 1008 (shown in FIGS. 2 and 10, respectively; not shown in        FIG. 17). Aperture layer 1740 is configured to receive the input        marginal ray lines 1733. The term “optically transparent” herein        refers to as allowing most or all light to pass through. Light        herein refers to spectrum of light in the near-ultraviolet,        visible, and near-infrared range (e.g. 300 nm to 5000 nm).        Optically non-transparent herein refers to as allowing little to        no light to pass through, but rather absorbing or reflecting the        light. Aperture layer 1740 can include optically transparent        apertures separated from each other by optically non-transparent        stop regions. The apertures and stop regions can be built upon a        single monolithic piece such as an optically transparent        substrate. Aperture layer 1740 can optionally include a        one-dimensional or two-dimensional array of apertures 1744.    -   An optical lens layer 1750 including a collimating lens 1751        characterized by a focal length, offset from the plane of        aperture 1744 and stop region 1746 by the focal length, aligned        axially with aperture 1744, and configured to collimate photons        passed by the aperture such that they are traveling        approximately parallel to the axis of collimating lens 1751        which is aligned with the optical axis of receiver channel 1700.        Optical lens layer 1750 may optionally include apertures,        optically non-transparent regions and tube structures to reduce        cross talk.    -   An optical filter layer 1760 including an optical filter 1761,        typically a Bragg reflector type filter, adjacent to collimating        lens 1751 and opposite of aperture 1744. Optical filter layer        1760 can be configured to pass normally incident photons at a        specific operating wavelength and passband. Optical filter layer        1760 may contain any number of optical filters 1761. Optical        filter layer 1760 may optionally include apertures, optically        non-transparent regions and tube structures to reduce cross        talk.    -   A photosensor layer 1770 including a photosensor 1771 adjacent        to optical filter layer 1760 and configured to detect photons        incident on photosensor 1771. Photosensor 1771 herein refers to        a single photodetector capable of detecting photons, e.g., an        avalanche photodiode, a SPAD (Single Photon Avalanche Detector),        RCP (Resonant Cavity Photo-diodes), and the like, or several        photodetectors, such as an array of SPADs, cooperating together        to act as a single photosensor, often with higher dynamic range,        lower dark count rate, or other beneficial properties as        compared to a single large photon detection area. Each        photodetector can be an active area that is capable of sensing        photons, i.e., light. Photosensor layer 1770 refers to a layer        made of photodetector(s) and contains optional structures to        improve detection efficiency and reduce cross talk with        neighboring receiver structures. Photosensor layer 1770 may        optionally include diffusers, converging lenses, apertures,        optically non-transparent tube spacer structures, optically        non-transparent conical spacer structures, etc.

Stray light may be caused by roughness of optical surfaces,imperfections in transparent media, back reflections, and the like, andmay be generated at many features within the receiver channel 1700 orexternal to receiver channel 1700. The stray light may be directed:through the filter region 1761 along a path non-parallel to the opticalaxis of collimating lens 1751; reflecting between aperture 1744 andcollimating lens 1751; and generally taking any other path or trajectorypossibly containing many reflections and refractions. If multiplereceiver channels are arrayed adjacent to one another, this stray lightin one receiver channel may be absorbed by a photosensor in anotherchannel, thereby contaminating the timing, phase, or other informationinherent to photons. Accordingly, receiver channel 1700 may featureseveral structures to reduce crosstalk between receiver channels.

As will be understood further herein, each layer of a micro-opticchannel layer structure can be designed a specific way to mitigate thedetrimental effects of stray light. Various different designs for eachlayer will now be discussed in further detail below.

A. Aperture Layer

In an embodiment having aperture layer 1740, as shown in FIG. 17,optically transparent aperture 1744 and optically non-transparent stopregion 1746 can be formed from a single monolithic piece, such as ametal foil with a pinhole or from a single layer of a deposited opaqueor reflective material having apertures etched therethrough.

FIG. 18A is a simplified cross-sectional view diagram of a differentembodiment 1800 where aperture layer 1840 has two apertures 1844. Boththe optically transparent apertures 1844 and corresponding opticallynon-transparent optical stop regions 1846 are supported on an opticallytransparent substrate 1845. Bottom aperture 1844 can be smaller and bepositioned at the focal plane of the bulk optic. Aperture layer 1840 canbe followed by optically transparent spacer structure 1856 positionedbetween aperture 1844 and collimating lens 1851 in the receiver channel.Optically transparent spacer structure 1856 forms a tube ofsubstantially similar or larger diameter to collimating lens 1851.

FIG. 18B is a simplified cross-sectional view diagram of a differentembodiment 1801 of aperture layer 1840. Optically transparent aperture1844 and optically non-transparent stop region 1846 are supported onoptically transparent substrate 1845. Optically transparent spacerstructure 1856 that follows aperture layer 1840 and positioned betweenaperture 1844 and collimating lens 1851 forms a tube of substantiallysimilar or larger diameter to collimating lens 1851.

FIG. 18C is a simplified cross-sectional view diagram of an embodiment1802 of aperture layer 1840 consisting of multiple opticallynon-transparent stop regions 1846 that are supported on opticallytransparent substrate 1845. These layers (stop regions 1846) follow thecontour of marginal light rays (not shown, but similar to light rays1733 in FIG. 17) to reduce stray light into the receiver channel.Optically transparent spacer structure 1856 below aperture layer 1840forms a tube of substantially similar or larger diameter to collimatinglens 1851.

FIG. 18D is a simplified cross-sectional view diagram of an embodiment1803 of aperture layer 1840 having multiple optically non-transparentstop layers 1846 supported on multiple optically transparent substrate1845. Aperture layer 1840 follows the contour of marginal light rays(not shown, but similar to light rays 1733 in FIG. 17) to reduce straylight into the receiver channel. Optically transparent spacer structure1856 below aperture layer 1840 forms a tube of substantially similar orlarger diameter to collimating lens 1851.

In some other embodiments of the present disclosure, spacer structure1856 shown in FIGS. 18A-D, can be optically non-transparent. Theoptically non-transparent spacer structure in this instance could beformed by etching a silicon or glass wafer and may be coated with anoptically non-transparent material (e.g. black chrome). Additionally,the spacer structure in this instance would prevent any light in thespacer region from traveling outside the receiver channel.

B. Spacer Structure Between Aperture Layer and Optical Lens Layer

FIG. 19A is a simplified cross-sectional view diagram of an embodiment1900 of the present disclosure with an optically non-transparent spacerstructure between the aperture layer and the lens layer. FIG. 19Adepicts an optically non-transparent spacer structure 1956 positionedbetween aperture 1944 and collimating lens 1951 in the receiver channel.Optically non-transparent spacer structure 1956 forms a tube ofsubstantially similar or larger diameter to collimating lens 1951 andprevents any light from traveling outside the receiver channel in theregion between aperture 1944 and collimating lens 1951. Opticallynon-transparent spacer structure 1956 could be formed by etching asilicon or glass wafer and may be coated with an opticallynon-transparent material (e.g. black chrome). Alternatively, opticallynon-transparent spacer structure 1956 could be a solid non-transparentstructure that is fabricated from molded polymer or any other suitablemethod. FIG. 19A shows the aperture layer having optically transparentsubstrate 1945 on the top, followed by the optically non-transparentstop region 1946 and aperture 1944, and then by opticallynon-transparent spacer structure 1956.

FIG. 19B is a simplified cross-sectional view diagram of an embodiment1901 of the present disclosure with an optically non-transparentstructure between the aperture layer and the lens layer. FIG. 1901depicts an optically non-transparent spacer structure 1956 positionedbetween aperture 1944 and collimating lens 1951. Opticallynon-transparent spacer structure 1956 forms a tube of substantiallysimilar or larger diameter to collimating lens 1951 and prevents anylight from traveling outside of the receiver channel in the regionbetween aperture 1944 and collimating lens 1951. FIG. 19B shows multipleoptically non-transparent stop regions 1946 supported on opticallytransparent substrate 1945.

FIG. 19C is a simplified cross-sectional view diagram of an embodiment1902 of aperture layer 1940 where aperture 1944 is conically aligned,and where the conical structure as an optically non-transparent layercoated on an optically transparent material.

FIG. 19D is a simplified cross-sectional view diagram of an embodiment1903 of aperture layer 1940 where the aperture 1944 is conicallyaligned, and where the conical structure is a solid structure formed ofan optically non-transparent material. As shown in FIGS. 19C and 19D theoptically transparent aperture 1944 and optically non-transparent stopregion 1946 are combined into a monolithic layer with a conical cavityaligned with the optical axis of the receiver channel and configured toconform to the shape of marginal ray lines (not shown, but similar tolight rays 1733 in FIG. 17).

C. Optical Filter Layer

FIG. 20A is a simplified cross-sectional view diagram of an embodiment2000 of filter layer 2060 for a receiver channel, according to someembodiments of the present disclosure. Optical filter layer 2060 caninclude a single optical filter 2061 supported on an opticallytransparent substrate 2065. Optical filter layer 2060 can be placed ontop of optically transparent substrate 2065 or below opticallytransparent substrate 2065. Optical filter 2061 can be a bandpass filterthat blocks incident light outside of a defined set of wavelengths (e.g.945-950 nm). However, in some other embodiments, optical filter 2061 canbe an edge pass filter or any other suitable type of filter thatselectively allows light within a wavelength range to pass throughitself.

FIG. 20B is a simplified cross-sectional view diagram of an embodiment2001 of filter layer 2060 for a receiver channel, according to someembodiments of the present disclosure. Optical filter layer 2060 caninclude two optical filters 2061 sandwiching and supported by anoptically transparent substrate 2065. Optical filter layer 2060 cancontain any number of optical filters 2061 on any number of substrates2065. One of the optical filters 2061 as shown in FIG. 20B can be abandpass filter and can be positioned on either on top of or directlybelow optically transparent substrate 2065 that blocks all of theincident light for a defined set of wavelengths (e.g. 900-945 nm and950-995 nm). The other optical filter 2061 placed on the opposite sideof the optical substrate 2065 can be a wide spectrum blocking filter(except for the region covered by the bandpass filter), for examplecovering 200-915 nm and 980-1600 nm. The bandpass filter and blockingfilter are designed such that there is no leakage in the transitionregion between the two filters. However, the filters could be two edgepass filters designed to work in conjunction as a bandpass filter or anyother types of filters.

In some other embodiments of the present disclosure, the bandpass filterand wide spectrum blocking filter are merged into a single opticalfilter 2061 and placed on either the top or bottom of optically clearsubstrate 2065.

1. Filter Layer with Apertures

FIG. 20C is a simplified cross-sectional view diagram of an embodiment2002 of filter layer 2060 for a receiver channel, according to someembodiments of the present disclosure. Optical filter layer 2060 canhave an additional aperture 2049 on top and an additional aperture 2054on the bottom of optical filter layer 2060 along with the correspondingoptically non-transparent stop regions 2063 & 2055. Aperture 2049defines the maximal cylinder of light desired to be passed into opticalfilter layer 2060 by optical filter 2061, and stop region 2063 an absorbor reflect any incident stray light outside the diameter of aperture2049. Aperture 2054 defines the maximal cylinder of light desired to bepassed out of optical filter layer 2060 and stop region 2055 absorbs orreflects any incident stray light outside the diameter of aperture 2054.Optical filters 2061 can be supported on an optically transparentsubstrate 2065.

In some embodiments of the present disclosure, filter layer 2060 canhave a single aperture 2049 placed on the top of the optical filterlayer 2060. In some additional and alternative embodiments of thepresent disclosure, filter layer 2060 can have a single aperture 2054placed on the bottom of optical filter layer 2060.

FIG. 20D is a simplified cross-sectional view diagram of an embodiment2003 of filter layer 2060 for a receiver channel, according to someembodiments of the present disclosure. Optical filter layer 2060 caninclude multiple optically transparent substrates 2065, and multipleoptically non-transparent aperture layers between them in an alternatingorder. FIG. 20D shows an additional aperture 2049 and correspondingoptically non-transparent stop region 2063 positioned on top of opticalfilter 2061 and supported by optically transparent substrates 2065.Aperture 2049 can define the maximal cylinder of light desired to bepassed into optical filter layer 2060 by optical filter 2061, and stopregion 2063 absorbs or reflects any incident stray light outsidediameter of aperture 2049. FIG. 20D shows an additional aperture 2054and corresponding optically non-transparent stop region 2055 positionedbetween optical filter layer 2060 and a photosensor layer (not shown,but similar to photosensor layer 1770 in FIG. 17). Aperture 2054 candefine the maximal cylinder of light desired to be passed out of opticalfilter layer 2060 toward the photosensor, and stop region 2055 canabsorb or reflect any incident stray light outside the diameter ofaperture 2054. Collectively, these interleaved layers prevent straylight in one optical filter layer 2060 from traveling into an opticalfilter region of an adjacent receiver channel in a multi receiverchannel system.

2. Filter Layer with Tube Structure

FIG. 20E is a simplified cross-sectional view diagram of an embodiment2004 of filter layer 2060 for a receiver channel, according to someembodiments of the present disclosure. Optical filter layer 2060 caninclude optical filter 2061 and optically transparent substrate 2065 andbe surrounded by an optically non-transparent tube structure 2111, whichprevents stray light in one optical filter layer 2060 from travelinginto an optical filter region of an adjacent receiver channel in a multireceiver channel system. Tube structure 2111 can be formed of a varietyof materials, including but not limited to silicon, metals, polymers, orglasses.

FIG. 20F is a simplified cross-sectional view diagram of an embodiment2005 of filter layer 2060 for a receiver channel, according to someembodiments of the present disclosure. Optical filter layer 2060 caninclude optical filter 2061 and optically transparent substrate 2065 andis surrounded by an optically non-transparent tube structure 2111, whichprevents stray light in one optical filter layer 2060 from travelinginto an optical filter region of an adjacent receiver channel in a multireceiver channel system. Tube structure 2111 can be formed of a varietyof materials, including but not limited to silicon, metals, polymers, orglasses. As shown in FIG. 20F, tube structure 2111 may only passpartially through optical filter layer 2060. This type of structure canbe formed by performing deep anisotropic etches on each side of filtersubstrate 2065 and selectively depositing metal or polymer afterwards.

FIG. 20G is a simplified cross-sectional view diagram of an embodiment2006 of filter layer 2060 for a receiver channel, according to someembodiments of the present disclosure. Optical filter layer 2060 caninclude two optical filters 2061 supported on optically transparentsubstrates 2065 and surrounded by an optically non-transparent tubestructure 2111, which prevents stray light in one optical filter layer2060 from traveling into an optical filter region of an adjacentreceiver channel in a multi receiver channel system. However, theoptical filter region may contain any number of optical filters 2061 onany number of substrates 2065 within the optical filter layer 2060. FIG.20G illustrates an additional aperture 2049 and corresponding opticallynon-transparent stop region 2063 positioned on top of optical filter2061 and supported by optically transparent substrate 2065. Aperture2049 can define the maximal cylinder of light desired to be passed intooptical filter layer 2060 and stop region 2063 can absorb or reflect anyincident stray light outside the diameter of aperture 2049.

Embodiment 2006 of optical filter layer 2060 in FIG. 20G can have anadditional aperture 2054, and corresponding optically non-transparentstop region 2055 can be positioned between optical filter layer 2060 andthe photosensor layer (not shown, but similar to photosensor layer 1770in FIG. 17). Aperture 2054 can define the maximal cylinder of lightdesired to be passed out of optical filter layer 2060 toward thephotosensor, and stop region 2055 can absorb or reflect any incidentstray light outside the diameter of aperture 2054. Tube structure 2111can be formed of a variety of materials, including but not limited tosilicon, metals, polymers, or glasses.

D. Photosensor Layer

As can be appreciated herein, various different photosensor layerdesigns can be implemented in a micro-optic receiver channel.

1. Photosensor Layer with Diffuser

FIG. 21A is a simplified cross-sectional view diagram of an embodiment2100 of receiver channel 2132 containing an optional diffuser 2181located in photosensor layer 2170 between optical filter 2161 andphotosensor 2173, according to some embodiments of the presentdisclosure. Diffuser 2181 can be configured to spread collimated photonsthat are output from collimating lens 2151 and passed by optical filterregion 2160, across the full width of a corresponding photosensor 2173.Photosensor 2173 may be non-square or non-circular in geometry (e.g.,short and wide) in order to extend the sensing area of photosensor 2173to be wider or taller than width or height of the other components inreceiver channel 2132.

Diffuser 2181 is configured to spread light rays across the area ofphotosensor 2173 such that photosensor 2173 is able to detect theincident photons across its full width and height, thereby increasingthe dynamic range of receiver channel 2132, even where the overallheight of receiver channel 2132 has to be limited for practicalconsiderations. In particular, in this embodiment, receiver channel 2132may include widened photosensors exhibiting greater photodetectors 2171(i.e., areas sensitive to incident photons) and a diffuser 2181 arrangedover photosensor 2173 that spreads light passed by optical filter 2161across the full area of photosensor 2173, thereby yielding increaseddynamic range.

In some embodiments, photosensor 2173 includes an array of single-photonavalanche diode detectors 2171 (hereinafter “SPADs”). The height andwidth of the receiver channel (usually defined by the diameter ofcollimating lens 2151) may accommodate only a relatively small number of(e.g., two) vertically-stacked SPADs. Photosensor 2173 can thereforedefine an aspect ratio greater than 1:1, and diffuser 2181 can spreadlight rays passed by the optical filter region 2160 according to thegeometry of photosensor 2173 in order to accommodate a larger sensingarea per photosensor. By incorporating more SPADs per photosensor, thedynamic range of the photosensor can be increased, as it less likely forall SPADs to be unable to detect photons (i.e., to be “dead”)simultaneously.

In some other embodiments, photosensor 2173 includes an array ofphotodetectors 2171. The height and width of the receiver channel(usually defined by the diameter of collimating lens 2151) mayaccommodate only a relatively small number of (e.g., two)vertically-stacked photodiodes. Photosensor 2173 can therefore define anaspect ratio greater than 1:1, and diffuser 2181 can spread light rayspassed by the optical filter region 2160 according to the geometry ofphotosensor 2173 in order to accommodate a larger sensing area perphotosensor. By incorporating more photodiodes per photosensor, thedynamic range of the photosensor can be increased, as it is unlikely forall photodiodes to be saturated simultaneously.

Receiver channel 2132 can additionally or alternatively include anaperture layer interposed between optical filter region 2160 anddiffuser 2181 or between the optical filter region 2160 and photosensor2173, where aperture 2144 is aligned with a corresponding collimatinglens 2151. In this variation, aperture 2144 can absorb or reflect errantlight rays passed by the light filter or reflected by the photosensor tofurther reduce crosstalk between receiver channels, thereby furtherincreasing SNR (Signal to Noise Ratio) of the system.

2. Photosensor Layer with Converging Lens Set

FIG. 21B is a simplified cross-sectional view diagram of an embodiment2101 of receiver channel 2132, according to some embodiments of thepresent disclosure. A photosensor layer 2170 of embodiment 2100 caninclude a photosensor 2173 formed of a set of discrete photodetectors2171 (e.g., SPADs) and a set of inactive regions 2172 (e.g., integratedlogic) encompassing the set of photodetectors, where each photodetectoris configured to detect incident photons. Photosensor layer 2170 canalso include a converging lens set 2191 interposed between opticalfilter region 2160 and photosensor 2173 with photodetectors 2171, andincluding one converging lens 2191 per discrete photodetector 2171within photosensor 2173, where each lens of the converging lens set 2191is configured to focus incident photons passed by optical filter region2160 onto a corresponding discrete photodetector 2171. Each converginglens can exhibit a common focal length, and converging lens set 2191 canbe offset above photosensor 2173 by this common focal length (or by adistance substantially similar to this common focal length), and eachconverging lens can converge incident light—collimated in optical lenslayer 2150 and passed by optical filter region 2160—onto a correspondingphotodetector 2171 in photosensor 2173.

In some embodiments, converging lens set 2191 interposed between opticalfilter region 2160 and photosensor 2173 with photodetectors 2171 employsdiffracting elements in addition to or replacement of refractiveelements.

3. Photosensor Layer with Converging Lens Set and Additional Apertures

FIG. 21C is a simplified cross-sectional view diagram of an embodiment2102 of photosensor layer 2170, according to some embodiments of thepresent disclosure. Photosensor layer 2170 can include a converging lensset 2191, and a set of apertures 2157, wherein each aperture 2157 isaligned with a corresponding converging lens 2191. In this variation,each aperture 2157 can absorb or reflect errant light rays passed by thelight filter or reflected by the photosensor to further reduce crosstalkbetween receiver channels, thereby further increasing the SNR of thesystem. Set of apertures 2157 and corresponding opticallynon-transparent stop regions 2159 are built on an optically transparentsubstrate 2158.

FIG. 21D is a simplified cross-sectional view diagram of an embodiment2103 of photosensor layer 2170, according to some embodiments of thepresent disclosure. Photosensor layer 2170 can include converging lensset 2191, and set of apertures 2157, where each aperture 2157 is alignedwith a corresponding converging lens 2191. Apertures 2157 andcorresponding optically non-transparent stop regions 2159 are built onan optically transparent substrate 2158. In this variation, apertures2157 do not go all the way through to photodetector 2171.

FIG. 21E is a simplified cross-sectional view diagram of an embodiment2104 of photosensor layer 2170, according to some embodiments of thepresent disclosure. An additional set of apertures 2157 andcorresponding optically non-transparent stop regions 2159 definingdesired maximal light cones can be positioned between lens set 2191 andphotodetector 2171. Set of apertures 2157 and correspondingnon-transparent stop regions 2159 define a light cone for every lens inlens set 2191 and function to absorb or reflect any stray lighttraveling along a path not encompassed by the desired light cones. Theapertures may be fabricated using standard semiconductor processes.

4. Photosensor Layer with Converging Lens Set and Spacer StructureBetween the Lens Set and the Photosensor

FIG. 21F is a simplified cross-sectional view diagram of an embodiment2105 of photosensor layer 2170, according to some embodiments of thepresent disclosure. Here, an optically non-transparent spacer structure2163 is positioned between lens set 2191 and photosensor 2173 havingphotodetectors 2171 in receiver channel 2132. Optically non-transparentspacer structure 2163 forms a tube of substantially similar or largerdiameter to a collimating lens (e.g., collimating lens 1751 shown inFIG. 17) and prevents any light from traveling outside of receiverchannel 2132 in the region between lens set 2191 and photosensor 2173.Optically non-transparent spacer structure 2163 could be made fromoptically non-transparent bulk media (e.g. silicon or polymer).

FIG. 21G is a simplified cross-sectional view diagram of an embodiment2106 of photosensor layer 2170, according to some embodiments of thepresent disclosure. Here, optically non-transparent spacer structure2163 is positioned between lens set 2191 and photosensor 2173, and ismade from an optically non-transparent coating on an opticallytransparent substrate (e.g. black chrome on glass). Opticallynon-transparent spacer structure 2163 forms a tube of substantiallysimilar or larger diameter to collimating lens 2151 and prevents anylight from traveling outside of receiver channel 2132 in the regionbetween lens set 2191 and photodetector 2171.

5. Photosensor Layer Spacer Structure Between the Filter Layer and thePhotosensor Layer

FIG. 21H is a simplified cross-sectional view diagram of an embodiment2107 of photosensor layer 2170, according to some embodiments of thepresent disclosure. Optically non-transparent spacer structure 2163 canbe positioned between an optical filter layer (e.g., any of theabove-mentioned optical filter layers) and photosensor layer 2170.Optically non-transparent spacer structure 2163 forms a tube ofsubstantially similar or larger diameter to a collimating lens (e.g.,collimating lens 1751 in FIG. 17) and prevents any light from travelingoutside of the receiver channel (e.g., channel 1700 in FIG. 17) in theregion between the optical filter layer and photosensor layer 2170.Optically non-transparent spacer structure 2163 can be formed by etchinga silicon or glass wafer and may be coated with an opticallynon-transparent material (e.g. black chrome). Alternatively, opticallynon-transparent spacer structure 2163 can be fabricated from moldedpolymer. In this embodiment, lens set 2191 is directly bonded tophotosensor 2173. Similar to its function in previous embodiments, lensset 2191 serves to focus light onto photodetectors 2171 of photosensor2173, rather than the inactive areas. These lenses could be integrateddirectly on top of an ASIC containing photosensor 2173 in a waferfabrication process, easing production.

6. Photosensor Layer with Conical Spacer Structures

FIG. 21I is a simplified cross-sectional view diagram of an embodiment2108 of photosensor layer 2170, according to some embodiments of thepresent disclosure. In this embodiment, photosensor layer 2170 includesa set of conical, optically non-transparent spacer structures 2164 thatis positioned between a lens set (not shown but, e.g., lens set 2191 inFIGS. 21F and 21G) and photosensor 2173. Set of conical, opticallynon-transparent spacer structures 2164 can form tapered tubes, each withsubstantially similar entrance diameter to individual lenses in the lensset, and each with substantially similar exit diameter to the individualphotodetectors 2171 of photosensor 2173. Set of conical, opticallynon-transparent spacer structures 2164 prevents any light from travelingoutside of the receiver channel in regions between the lens set andphotosensor 2173 and also guide light toward the photodetectors 2171 ofphotosensor 2173. The set of conical, optically non-transparent spacerstructures 2164 can be formed by etching a silicon or glass wafer andmay be coated with an optically non-transparent material (e.g. blackchrome). Alternatively, set of conical, optically non-transparent spacerstructures 2164 can be fabricated from molded polymer.

FIG. 21J is a simplified cross-sectional view diagram of an embodiment2109 of photosensor layer 2173, according to some embodiments of thepresent disclosure. In this embodiment, photosensor layer 2173 includesa set of conical, optically non-transparent spacer structures 2164 thatis positioned between a lens set (not shown but, e.g., lens set 2191 inFIGS. 21F and 21G) and photodetector 2171. The inner walls of the set ofconical, optically non-transparent spacer structures 2164 are coatedwith a reflective material (e.g. chrome) in order to further enhance thestructures' ability to act as a light pipe. Set of conical, opticallynon-transparent spacer structures 2164 form tapered tubes, each withsubstantially similar entrance diameter to individual lenses in the lensset, and each with substantially similar exit diameter to the individualphotodetectors 2171 of photosensor 2173. Set of conical, opticallynon-transparent spacer structures 2164 prevents any light from travelingoutside of the receiver channel in regions between the lens set andphotosensor 2171 and also guide light toward the photodetectors 2171 ofphotosensor 2173.

7. Photosensor Layer with Resonant Photo-Cavity Diodes

FIG. 21K is a simplified cross-sectional view diagram of a receiverchannel 2132 including an embodiment 2110 of photosensor layer 2170,according to some embodiments of the present disclosure. In thisembodiment, photosensor layer 2170 is configured with a resonant cavityaround a photo sensitive diode to improve the photon detectionefficiency. Each photosensor 2173 includes one or more resonantphoto-cavity diodes. Each photosensor 2173 includes one or morephoto-diodes 2174 (photodetectors) along with highly-reflective (e.g.,partially-mirrored) surfaces facing the top and bottom of the area (theresonant cavity). Generally, an photodetector of a non-resonant cavitydiode may have a relatively low quantum efficiency. To improve thepercentage of photons detected by the photodetector, resonantphoto-cavity diode 2174 is used that includes: a first mirrored surface2175 below and facing the photodetector; and a second partially mirroredsurface 2176 above and facing the photodetector, that also allows lightto enter the cavity as shown in FIG. 21K. Thus, when a photon passesthrough and is not detected by an photodetector of resonant photo-cavitydiode 2174, first mirrored surface 2175 surrounding the photodetector ofresonant photo-cavity diode 2174 reflects the photon back toward topreflective surface 2176 of the cavity and through the photodetectoragain, which may detect the photon upon its second transition throughthe photodetector. However, if the photodetector fails to detect thephoton upon this second collision, the reflection process is repeatedwith the second mirrored surface reflecting the photon back toward thephotodetector, which again may detect the photon upon its thirdcollision with the photodetector. This process may repeat until thephoton is detected by the photodetector of the photosensor or the photonescapes or is absorbed by the cavity. Resonant photo-cavity diode 2174can thus achieve a relatively high rate of photon detection (i.e.approaching 100%). Note that a particle interpretation of light is usedin the preceding description, but consideration of wave interferenceeffects are critical for a complete description of resonant cavityphotodiodes. Also note that the active region of resonant photo-cavitydiode 2174 may be comprised of a standard photodiode, an avalanchephotodiode, a SPAD, or any other photosensor.

FIG. 21K further shows that one or more resonant cavity photodiodes (or“RCPs”) 2174 may be combined with aperture 2144, collimating lens 2151,optical filter region 2160, and any combination of the aforementioneddiffusers, converging lens sets, or crosstalk mitigation structures toform a variant of receiver channel 2132. A typical RCP will have similarwavelength sensitivity as optical filter region 2160 and can be designedto be sensitive to a similar set of wavelengths of light as opticalfilter region 2160. However, due to fabrication or other limitations,the RCP may have more part-to-part variability of the center wavelengthof the RCP's operating spectrum and thus necessitate a broader operatingwavelength band in order for every photosensor to be capable ofdetecting photons at the system's operating wavelength. Alternatively,it may simply be impossible to reliably fabricate an RCP with anoperating wavelength band as narrow as the filter passband. Forinstance, optical filter region 2160 may have a passband as narrow as0.1 nm, while the RCP may have an operating band of 10 nm. With theoptical filter region 2160 on top of the RCP 2174, the combined filterand RCP system has an effective operating wavelength band substantiallysimilar to optical filter region 2160. In addition, the RCP performanceis improved when sensing collimated light, as opposed to focused light,which is provided as a result of collimating lens 2151 as depicted inFIG. 21K. In this way, a system employing aperture 2144, collimatinglens 2151, optical filter region 2160, and RCP 2174 may achieve highphoton detection efficiency and narrow wavelength selectivity tomaximize the SNR within receiver channel 2132.

E. Hemispherical Receiver Structures

FIG. 22A is a simplified cross-sectional view diagram of an embodiment2200 of a receiver channel 2232, according to some embodiments of thepresent disclosure. Receiver channel 2232 of embodiment 2200 can includeconvex hemispheres supported on an optically non-transparent material.In this embodiment, an aperture layer 2240 is combined with an opticalfilter 2261 coated on a convex hemisphere 2267, with the center ofhemisphere 2267 located at or near the focal point of incoming light(marginal ray lines 2233). The center of hemisphere 2267 alsocorresponds to, or nearly corresponds to, the center of aperture 2244.In some embodiments, hemisphere 2267 can be below aperture 2244, asshown in FIG. 22A. An advantage of the embodiment is that for asufficiently well-focused cone of rays, any ray lines 2233 will passthrough optical filter 2261 normal to the filter's surface, therebyeliminating CWL (Center Wave Length) shift due to variations in incidentangle of the light (e.g. light rays 2233) on optical filter 2261,thereby allowing the use of very narrow bandpass (e.g. 850-852 nm)filters.

This is further illustrated in FIG. 22B, which is a simplifiedcross-sectional view diagram of an embodiment 2201 of receiver channel2232, according to some embodiments of the present disclosure. Unlikeembodiment 2200 in FIG. 22A, embodiment 2201 in FIG. 2B can beconfigured so that hemisphere 2267 is positioned above aperture 2244 toachieve similar functionality but with a less compact footprint. Asshown in FIG. 22B, the angle of incidence on optical filter 2261 isnormal for marginal ray lines 2233 (and all other ray lines not shownexplicitly in FIG. 22B) that pass through the center of hemisphere 2267.Note that, while not shown in FIG. 22B or 22C, the rays will refractupon exiting the hemisphere structure since they are not normal to theplanar exit surface. Similarly, in FIG. 22A, there will be some amountof refraction when rays enter the flat side of the hemisphericalstructure.

As illustrated in FIGS. 22A to 22B, receiver channel 2232 includessidewalls 2263 between optically non-transparent stop region 2246 andphotosensor layer 2270 with photodetectors 2271 to reduce crosstalk.Sidewalls 2263 can be made up of optically non-transparent material ormade up of optically transparent material. In addition, sidewalls 2263can also be coated with reflective or absorptive material.

A close-up view of the convex hemispherical surface is shown in FIG.22C, which is a simplified cross-sectional view diagram of convexhemisphere 2267 of FIGS. 22A and 22B. Convex hemisphere 2267 can becoated with optical filter 2261 and positioned on a self-supporting,optically non-transparent stop region 2246 such as metal, silicon,polymer etc. In some embodiments where the convex hemispherical surfacesof the micro-optic channels are used for hyperspectral imagers, opticalfilter 2261 can be configured to be non-uniform. For example, opticalfilter 2261 can be a graduated filter increasing gradually or in astep-wise manner in one direction (e.g., the thickness direction) thatdifferent micro-optic channels have different optical filter layers thathave different thicknesses. This allows different micro-optic channelsto measure a different range of wavelengths as discussed herein withrespect to FIGS. 3A and 3B.

FIG. 22D is a simplified cross-sectional view diagram of an embodiment2202 of a receiver channel 2232, according to some embodiments of thepresent disclosure. Receiver channel 2232 of embodiment 2202 can includeconvex hemisphere 2267 supported on a rigid optically transparent layer.In this embodiment, aperture layer 2240 is combined with optical filter2261 and coated on convex hemisphere 2267, where the center ofhemisphere 2267 is located at or near the focal point of incoming light(ray lines 2233). The center of hemisphere 2267 also corresponds to, ornearly corresponds to, the center of the aperture 2244. As shown in FIG.22D, hemisphere 2267 can be below aperture layer 2240. In some otherembodiments, hemisphere 2267 can be above aperture layer 2240, as shownin FIG. 22E.

FIG. 22E is a simplified cross-sectional view diagram of an embodiment2203 of a receiver channel 2232, according to some embodiments of thepresent disclosure. Unlike embodiment 2202 in FIG. 22D, embodiment 2215in FIG. 2E can be configured so that hemisphere 2267 is positioned aboveaperture 2244 to achieve similar functionality as embodiment 2202 butwith a more compact footprint.

FIGS. 22D and 22E show convex hemisphere 2267 as being coated withoptical filter 2261 and imprinted on aperture layer 2240 that issupported on a rigid optically transparent layer 2245 (e.g. glass,polymer) with aperture 2244 along with the corresponding opticallynon-transparent stop regions 2246. As illustrated in FIGS. 22D and 22E,receiver channel 2232 includes sidewalls 2263 between opticallytransparent layer 2245 and photosensor layer 2270 with photodetectors2271 to reduce crosstalk. Sidewalls 2263 can be made up of opticallynon-transparent material or made up of optically transparent material.In addition, sidewalls 2263 can also be coated with reflective orabsorptive material. Note that, while not shown in FIGS. 22D and 22E,there may be refraction of rays 2233 entering and exiting the rigidoptically transparent layer 2245.

FIG. 22F is a simplified cross-sectional view diagram of an embodiment2204 of a receiver channel 2232, according to some embodiments of thepresent disclosure. Embodiment 2204 can include a concave hemisphere2267 made of optically transparent material (e.g. glass, polymer) with acoated optical filter 2261. Self-supported aperture layer 2240 canoverhang concave hemisphere 2267 and can be perforated or etched with anoptically non-transparent rigid material (e.g. metal film) to form theoptically non-transparent stop regions 2246. As shown in FIG. 22F,hemisphere 2267 can be positioned below aperture layer 2240. The centerof aperture 2244 can be located at or near the focal point of theincoming light (rays 2233). Additionally, the center of the hemisphere2267 can be located at or near the focal point of the incoming light(rays 2233). As illustrated in FIG. 22F, receiver channel 2232 includessidewalls 2263 between optically transparent layer 2245 and photosensorlayer 2270 with photodetectors 2271 to reduce crosstalk. Sidewalls 2263can be made up of optically non-transparent material or made up ofoptically transparent material. In addition, sidewalls 2263 can also becoated with reflective or absorptive material.

FIG. 22G is a simplified cross-sectional view diagram of an embodiment2205 of receiver channel 2232, according to some embodiments of thepresent disclosure. Unlike embodiment 2204 in FIG. 22F, embodiment 2205in FIG. 2G can be configured so that hemisphere 2267 is positioned aboveaperture 2244 to achieve similar functionality as embodiment 2204, butembodiment 2204 may have a more compact footprint.

FIG. 22H is a simplified cross-sectional view diagram of an embodiment2206 of receiver channel 2232, according to some embodiments of thepresent disclosure. Receiver channel 2232 of embodiment 2206 can includea concave hemisphere 2267 and aperture layer 2240 supported by a rigid,optically transparent layer 2245. In some embodiments, concavehemisphere 2267 can be below the aperture layer 2240 as shown in FIG.22H. Concave hemisphere 267 can be made of optically transparentmaterial (e.g. glass, polymer) with a coated optical filter 2261.Aperture layer 2240 with optically transparent aperture 2244 andcorresponding optically non-transparent stop regions 244 is supported byoptically transparent layer 2245 on both top and bottom sides ofaperture layer 2240. The center of aperture 2244 is located at or nearthe focal point of the incoming light (rays 2233). Additionally, thecenter of concave hemisphere 2267 is located at or near the focal pointof the incoming light (rays 2233). As illustrated in FIG. 22H, receiverchannel 2232 includes sidewalls 2263 between optically transparent layer2245 and photosensor layer 2270 with photodetectors 2271 to reducecrosstalk. Sidewalls 2263 can be made up of optically non-transparentmaterial or made up of optically transparent material. In addition,sidewalls 2263 can also be coated with reflective or absorptivematerial.

FIG. 22I is a simplified cross-sectional view diagram of an embodiment2207 of receiver channel 2232, according to some embodiments of thepresent disclosure. Unlike embodiment 2206 in FIG. 22H, embodiment 2207in FIG. 21 can be configured so that hemisphere 2267 is positioned aboveaperture 2244 to achieve similar functionality as embodiment 2206.

F. Bottom Micro-Lens Layer

FIG. 23A is a simplified cross-sectional view diagram of an embodiment2300 of a receiver channel 2332, according to some embodiments of thepresent disclosure. Receiver channel 2332 of embodiment 2300 can includea Bottom Micro-Lens Layer (BMLL), which consists of one or moremicro-lenses 2391 that are configured to guide divergent light rays intoactive portion of the photosensors. The BMLL performs ray anglecorrection to guide light from dissimilar angles into evenly spacedphotosensors. Ray angle correction can be achieved by controlling thelateral offset between lens center and the photosensor center, tiltingof the lens, or adjusting the form of the lens. A better illustration ofthis operation can be seen in FIG. 23B.

FIG. 23B is a simplified cross-sectional view diagram of a close-up viewof the propagation of light during ray angle correction by a BMLL,according to some embodiments of the present disclosure. As illustrated,the pitch of the micro-optics is either not constant or is not equal tothe pitch of lenses 2391 in order to steer the divergent rays (2333) toactive portions of photodetectors 2371 in the photosensor layer. Withreference back to FIG. 23A, each micro-lens 2391 can be positioned tocorrespond with a respective photodetector 2371.

FIG. 23C is a simplified cross-sectional view diagram of an embodiment2301 of a receiver channel 2332, according to some embodiments of thepresent disclosure. Receiver channel 2332 of embodiment 2301 can includea single micro-lens 2391, instead of a plurality of micro-lenses asshown in FIG. 23A. Single micro-lens 2391 can be positioned over andcentered to a single photodetector 2371. Micro-lens 2391 can beconfigured to guide light to single photodetector 2371.

FIGS. 23D and 23E is a simplified cross-sectional view diagram ofembodiments 2302 and 2303, respectively, of a receiver channel 2332,according to some embodiments of the present disclosure. Receiverchannel 2332 of embodiment 2302 can include a BMLL positioned on theunderside of an optically transparent layer 2345 supporting aperturelayer 2340 and hemisphere 2367 with optical filter 2361 coated. As shownin FIG. 23D, the BMLL can be formed of multiple lenses 2393 for guidingdivergent light to multiple photodetectors 2371. As shown in FIG. 23E,the BMLL can be formed of a single micro-lens 2391 for guiding divergentlight to photodetector 2371.

Embodiments 2302 and 2303 in FIGS. 23D and 23E each include a convexhemisphere 2367 supported on a rigid optically transparent layer 2345.In these illustrations, an aperture layer 2340 is combined with anoptical filter 2361 coated on hemisphere 2367, where the center ofhemisphere 2367 is located at or near the focal point of incoming light(marginal ray lines 2333). The center of hemisphere 2367 can alsocorrespond to, or nearly correspond to, the center of aperture 2344.Convex hemisphere 2367 can be coated with optical filter 2361 andimprinted on aperture layer 2340 that is supported on rigid opticallytransparent layer 2345 (e.g. layer formed of glass, polymer) and thecorresponding optically non-transparent stop regions 2346. Asillustrated in FIGS. 23D and 23E, receiver channel 2332 includessidewalls 2363 between optically transparent layer 2345 and photosensorlayer 2370 to reduce crosstalk. Sidewalls 2363 can be made up ofoptically non-transparent material or made up of optically transparentmaterial. In addition, sidewalls 2363 can also be coated with reflectiveor absorptive material.

G. Additional Exemplary Receiver Channels

It is to be appreciated that a receiver channel is a structure at themicro-optic level, e.g., a micro-optic receiver channel discussed above,that can be formed from multiple layers including one or more of anaperture layer, an optical lens layer below the aperture layer, anoptical filter layer below the aperture and optical lens layer, and aphotosensor layer below all the other layers. Each such layer can beconfigured in various ways to mitigate cross-talk. i.e., exposing straylight to adjacent receiver channels, as discussed herein with respect toFIGS. 17-23E. Various examples of receiver channels are discussed abovewith respect to FIGS. 17, 22A-22I, and 23A-23E. Two other examples ofreceiver channels according to the present disclosure are illustrated inFIGS. 24 and 25. Embodiments of the present disclosure are not limitedto the particular receiver channels described herein. Instead, based onthe present disclosure a person of skill in the art will appreciate thatin other embodiments a receiver channel according to the disclosure caninclude, among other options, an aperture layer as described above withrespect to any of FIG. 18A-18D or 19A-19D, a filter layer as describedabove with respect to any of FIGS. 20A-20G, and/or a photosensor layeras described above with respect to any of FIGS. 21A-21K.

FIG. 24 is a simplified cross-sectional view diagram of an exemplaryembodiment of a receiver channel 2400, according to some embodiments ofthe present disclosure. Receiver channel 2400 can include an aperturelayer 2440 composed of first and second apertures 2444, each formed inrespective optically non-transparent layers 2446 a and 2446 b. Firstand/or second apertures 2444 can be formed of void space defined byopenings within layers 2446 a and 2446 b in some embodiments, whilefirst and/or second apertures 2444 can be formed by opticallytransparent materials in some other embodiments. First and secondoptically non-transparent layers 2446 a and 2446 b can be supported byan optically transparent substrate 2445 sandwiched between first andsecond optically non-transparent layers 2446 a and 2446 b.

Receiver channel 2400 can also include an optical lens layer 2450disposed below aperture layer 2440. Optical lens layer 2450 can includea collimating lens 2451 and an optically non-transparent spacerstructure 2456. Collimating lens 2451 can be separated from aperturelayer 2440 by optically non-transparent spacer structure 2456. In someembodiments, optically non-transparent spacer structure 2456 forms atube having a circumference that surrounds collimating lens 2451 andextends toward aperture layer 2440. Optically non-transparent spacerstructure 2456 can be formed of an optically reflective or absorptivematerial that prevents any light from traveling outside of receiverchannel 2400 in the region between aperture layer 2440 and collimatinglens 2451.

In addition to aperture layer 2440 and optical lens layer 2450, receiverchannel 2400 can further include an optical filter layer 2460 positioneddirectly below optical lens layer 2450. Optical filter layer 2460 caninclude two optical filters 2461 sandwiching an optically transparentsubstrate 2465 that structurally supports optical filters 2461. Opticalfilter layer 2460 can contain any number and type of optical filters2461 on any number of substrates 2065. For instance, one of opticalfilters 2461 can be a bandpass filter and be positioned on either on topof or directly below optically transparent substrate 2465 that blocksall of the incident light for a defined set of wavelengths (e.g. 900-945nm and 950-995 nm). The other optical filter 2461 placed on the oppositeside of optically transparent substrate 2465 can be a different filter,such as a wide spectrum blocking filter (except for the region coveredby the bandpass filter), for example covering 200-915 nm and 980-1600nm. The bandpass filter and blocking filter are designed such that thereis no leakage in the transition region between the two filters. However,the filters could be two edge pass filters designed to work inconjunction as a bandpass filter or any other type of filter.

Immediately below optical filter layer 2460 can be a photosensor layer2470. In some embodiments, photosensor layer 2470 of embodiment 2400 caninclude an optically non-transparent spacer structure 2463 positionedbetween a converging lens set 2491 and a photosensor 2473. Photosensor2473 can be formed of a set of discrete photodetectors 2471 (e.g.,SPADs) positioned between a set of inactive regions 2172 (e.g.,integrated logic) in an alternating arrangement, where each discretephotodetector is configured to detect incident photons. Converging lensset 2491 can be interposed between optical filter layer 2460 andphotosensor 2473 with photodetectors 2471, and including one converginglens 2491 per discrete photodetector 2471 within photosensor 2173, whereeach lens of the converging lens set 2491 is configured to focusincident photons passed by optical filter layer 2460 onto acorresponding discrete photodetector 2471. Each converging lens canexhibit a common focal length, and converging lens set 2491 can beoffset above the sensing plane of the photosensor by this common focallength (or by a distance substantially similar to this common focallength), and each converging lens can converge incident light—collimatedin optical lens layer 2450 and passed by optical filter layer 2460—ontoone corresponding photodetector 2471 in photosensor 2473. Opticallynon-transparent spacer structure 2463 forms a tube of substantiallysimilar or larger diameter to a collimating lens 2451 and prevents anylight from traveling outside of receiver channel 2400 in the regionbetween lens set 2491 and photosensor 2473. Optically non-transparentspacer structure 2163 could be made from optically non-transparent bulkmedia (e.g. silicon or polymer).

Another exemplary embodiment of a receiver channel is shown in FIG. 25.FIG. 25 is a simplified cross-sectional view diagram of an exemplaryreceiver channel 2500, according to some embodiments of the presentdisclosure. Receiver channel 2500 can include an aperture layer 2540, anoptical lens layer 2550 disposed below aperture layer 2540, and anoptical filter layer 2560 below both aperture layer 2540 and opticallens layer 2550. Aperture layer 2540, optical lens layer 2550, andoptical filter layer 2560 can have the same construction and function ascorresponding components in FIG. 24.

Receiver channel 2500 can also include a photosensor layer 2570positioned immediately below optical filter layer 2560. In someembodiments, photosensor layer 2570 of embodiment 2400 can include anoptically non-transparent spacer structure 2563, a converging lens set2591, and a photosensor 2573. Unlike converging lens set 2491 ofreceiver channel 2400 in FIG. 24, converging lens set 2591 of receiverchannel 2500 can be positioned directly on at top surface of photosensor2573 instead of directly on an underside of optical filter layer 2560.Furthermore, optically non-transparent spacer structure 2563 can beformed of an optically non-transparent material (e.g., black chrome)coated on an optically transparent layer, such as a silicon or glasssubstrate, instead of being a solid optically non-transparent structure,e.g., optically non-transparent spacer structure 2463 of receiverchannel 2400 in FIG. 24. Lens set 2591 serves to focus light ontophotodetectors 2571 of photosensor 2573, rather than inactive areas2572.

By implementing a receiver channel according to any of embodiments 2400and 2500, errant light can be prevented from exposing on adjacentreceiver channels, thereby improving the accuracy of each photosensor'sability to capture photons for imaging.

VI. Micro Optical Receiver Channel Array Variations

According to some embodiments of the present disclosure, micro-opticalreceiver channels can be organized in an array. The array can havevarious dimensions according to design. For instance, an array ofmicro-optical receiver channels can be arranged in a M×N array where Mand N are equal to or greater than 1. Accordingly, micro-opticalreceiver channels can be one- and two-dimensional arrays, as will bediscussed furthered herein with respect to FIGS. 26-30, which illustratedifferent embodiments of micro-optical receiver channel arrays whereeach dot represents a micro-optical receiver channel. As aforementionedherein, each receiver channel can include a plurality of layers stackedupon each other. Thus, it can be appreciated that when arranged in anarray, each micro-optic receiver channel is part of a monolithic layercomposed of the individual elements reproduced many times in the M×Narrangement, e.g., an M×N aperture layer array, an M×N micro lens layerarray, and an M×N photosensor layer array. When bonded together, thesearray layers create a monolithic multi-channel micro optical receiverarray.

FIG. 26 is a simplified illustration of an exemplary micro-opticalreceiver array 2600, according to some embodiments of the presentdisclosure. Micro-optical receiver array 2600 is configured as a linear(M×1) array, specifically a 16×1 array. This layout can achieve a highresolution (e.g. 16×1024) as the implementation is amenable to scanningthe array in one dimension. As an example, for a receiver channel pitchof 500 microns the layout illustrated can be implemented in a chip of asize that is approximately 500 microns by 8000 microns.

FIG. 27 is a simplified illustration of an exemplary micro-opticalreceiver array 2700, according to some embodiments of the presentdisclosure. Micro-optical receiver array 2700 is configured as arectangular (M×N) array, specifically a 16×32 array. Thus, for areceiver channel pitch of 500 microns the layout illustrated can beimplemented in a chip of size 8,000 microns by 12000 microns.

FIG. 28 is a simplified illustration of an exemplary micro-opticalreceiver array 2800, according to some embodiments of the presentdisclosure. Micro-optical receiver array 2800 is configured as an M×Nstaggered array. In this illustration, receiver channels 2832 are laidout in a 16×4 staggered array. This layout can achieve a high resolution(e.g. 64×1024) as the implementation is amenable to sweeping. For areceiver channel pitch of 500 microns the layout illustrated in FIG. 28can be implemented in a chip of a size that is approximately 2000microns by 8375 microns.

FIG. 29 is a simplified illustration of an exemplary micro-opticalreceiver array 2900, according to some embodiments of the presentdisclosure. Micro-optical receiver array 2900 is configured as a warpedlinear (M×1) array. In this embodiment, the spacing between receiverchannels 2932 is uneven. Receiver channels near the center, shown as2932-01, are placed close together (e.g. 400 microns apart), while theexterior channels, shown as 2932-02, are placed farther apart (e.g.,greater than 400 microns apart), or vice versa. This layout has anadvantage of being able to allow for correction of the distortion curveof a lens (i.e. the angles between the receiver channel fields of vieware evenly spaced in the object space). The arrangement shown in FIG. 29can be used to achieve a high resolution (e.g. 16×1024) as theimplementation is amenable to sweeping. For an average receiver channelpitch of 500 microns the layout illustrated can be implemented in a chipof a size that is approximately 500 microns by 8000 microns.

In some embodiments, the receiver channels can be configured in a M×Nwarped array (where N≥1). In such embodiments, the receiver channels inthe center are placed further from each other in both the x and ydirection than the exterior receiver channels. This corrects for anotherpossible form of lens distortion.

FIG. 29 is a simplified illustration of an exemplary micro-opticalreceiver array 2900, according to some embodiments of the presentdisclosure. Micro-optical receiver array 2900 is configured in anarbitrary pattern. This layout arrangement has the advantage of beingable to accommodate lens distortion, to make adjustments to compensatefor any timing or routing variations, and also to match an arbitrarypattern from an illumination source.

Although the present disclosure has been described with respect tospecific embodiments, it will be appreciated that the present disclosureis intended to cover all modifications and equivalents within the scopeof the following claims.

What is claimed is:
 1. An optical system for performing distancemeasurements, the optical system comprising: a bulk transmitter optic;an illumination source comprising a plurality of light emitters alignedto project discrete beams of light through the bulk transmitter opticinto a field ahead of the optical system; and a micro-optic channelarray disposed between the illumination source and the bulk transmitteroptic, the micro-optic channel array defining a plurality of micro-opticchannels, each micro-optic channel including a micro-optic lens spacedapart from a light emitter from the plurality of light emitters with themicro-optic lens being configured to receive a light cone from the lightemitter and generate a reduced-size spot image of the emitter at a focalpoint displaced from the emitter at a location between the emitter andthe bulk transmitter optic.
 2. The optical system for performingdistance measurements set forth in claim 1 wherein the bulk transmitteroptic comprises one or more lenses configured as an image spacetelecentric lens in which the discrete beams of light output from theillumination source through the micro-optic channel array are parallelto each other.
 3. The optical system for performing distancemeasurements set forth in claim 2 further comprising a light sensingmodule configured to detect photons emitted from the illumination sourceand reflected from surfaces within the field.
 4. The optical system forperforming distance measurements set forth in claim 3 wherein the lightsensing module comprises: a bulk receiver optic; an aperture layerincluding a plurality of apertures; a lens layer including a pluralityof lenses; and a photosensor layer including a plurality ofphotosensors, wherein the aperture layer, lens layer, and photosensorlayer are arranged to form a plurality of receiver channels with eachreceiver channel in the plurality of receiver channels including anaperture from the plurality of apertures, a lens from the plurality oflenses and a photosensor from the plurality of photosensors and beingconfigured to communicate light incident from the bulk receiving opticto the photosensor of the receiver channel.
 5. The optical system forperforming distance measurements set forth in claim 4 wherein theillumination source is configured to selectively project the discretebeams of light through the bulk transmitter optic according to anillumination pattern that matches, in size and geometry across a rangeof distances from the system, the fields of view of the receiverchannels.
 6. The optical system for performing distance measurements setforth in claim 1 wherein the micro-optic lens for each channel isconfigured to receive a light cone from a light emitter and generate areduced-size real spot image of the emitter at a focal point between themicro-optic lens and the bulk transmitter optic.
 7. The optical systemfor performing distance measurements set forth in claim 6 wherein themicro-optic lens for each channel includes a first optical surface withan optical power on a side facing the light emitter and a second opticalsurface with an optical power on an opposing side facing away from thelight emitter and wherein the reduced-size real spot image of theemitter is formed at a focal point after the first and second opticalsurfaces.
 8. The optical system for performing distance measurements setforth in claim 7, wherein a divergence of the light cone from the lightemitter is less than a divergence of a light cone from the secondoptical surface of the micro-optic lens for generating the reduced-sizereal spot image.
 9. The optical system for performing distancemeasurements set forth in claim 7, wherein the micro-optic lens isseparated from the illumination source to define an open space betweenthe micro-optic lens and the illumination source.
 10. The optical systemfor performing distance measurements set forth in claim 6 wherein themicro-optic lens for each channel includes an optical surface with anoptical power on a side facing away from the light emitter and whereinthe reduced-size real spot image of the emitter is formed at a focalpoint after the optical surface.
 11. The optical system for performingdistance measurements set forth in claim 6 wherein the optical surfaceincludes a plurality of convex lenses positioned on a substrate, thesubstrate having a first surface upon which the optical surface isdisposed and a second surface opposite of the first surface that isdirectly attached to a surface of the illumination source.
 12. Theoptical system for performing distance measurements set forth in claim 1wherein the micro-optic lens for each channel is configured to receive alight cone from a light emitter and generate a reduced-size virtual spotimage of the emitter.
 13. The optical system for performing distancemeasurements set forth in claim 12 wherein the micro-optic lens for eachchannel includes an optical surface with an optical power on a sidefacing away from the light emitter and wherein the reduced-size virtualspot image of the emitter is formed at a focal point within therespective channel.
 14. The optical system for performing distancemeasurements set forth in claim 13 wherein the optical surface includesa plurality of concave surfaces formed on substrate, the substratehaving a first surface upon which the optical surface is disposed and asecond surface opposite of the first surface that is directly attachedto a surface of the illumination source.
 15. The optical system forperforming distance measurements set forth in claim 1 wherein the bulktransmitter optic comprises multiple aperture stops configured to reducestray light emitted by the optical system.
 16. An optical system forperforming distance measurements, the optical system comprising: a lightemission system comprising: a bulk transmitter optic; an illuminationsource comprising a plurality of light emitters aligned to projectdiscrete beams of light through the bulk transmitter optic into a fieldahead of the optical system; and a micro-optic channel array disposedbetween the illumination source and the bulk transmitter optic, themicro-optic channel array defining a plurality of micro-optic channels,each micro-optic channel including a micro-optic lens spaced apart froma light emitter from the plurality of light emitters with themicro-optic lens being configured to receive a light cone from the lightemitter and generate a reduced-size spot image of the emitter at a focalpoint displaced from the emitter at a location between the emitter andthe bulk transmitter optic; and a light detection system comprising: abulk receiver optic configured to receive the discrete beams of lightfrom the field; and an optical assembly having a plurality ofmicro-optic receiver channels defining a plurality of discrete,non-overlapping fields of view in the field, the optical assemblycomprising: an aperture layer having a plurality of discrete aperturesarranged along a focal plane of the bulk receiver optic; an array ofphotosensors disposed behind the aperture layer; and a plurality oflenses positioned between the aperture layer and the array ofphotosensors.
 17. The optical system for performing distancemeasurements set forth in claim 16 wherein the bulk transmitter opticcomprises one or more lenses configured as image space telecentric lensin which the discrete beams of light output from the illumination sourcethrough the micro-optic channel array are parallel to each other.
 18. Anoptical system for performing distance measurements, the optical systemcomprising: a stationary housing having an optically transparent window;and a light ranging device disposed within the housing, the lightranging device comprising an optical transmitter coupled to a platform,the optical transmitter comprising: a bulk transmitter optic; anillumination source comprising a plurality of light emitters aligned toproject discrete beams of light through the bulk transmitter optic intoa field ahead of the optical system; and a micro-optic channel arraydisposed between the illumination source and the bulk transmitter optic,the micro-optic channel array defining a plurality of micro-opticchannels, each micro-optic channel including a micro-optic lens spacedapart from a light emitter from the plurality of light emitters with themicro-optic lens being configured to receive a light cone from the lightemitter and generate a reduced-size spot image of the emitter at a focalpoint displaced from the emitter at a location between the emitter andthe bulk transmitter optic.
 19. The optical system for performingdistance measurements set forth in claim 18 wherein the light rangingdevice is a spinning light ranging device further comprising: a motordisposed within the housing and operatively coupled to spin the lightranging device including the platform and optical transmitter within thehousing; a system controller disposed within the housing, the systemcontroller configured to control the motor and to start and stop lightdetection operations of the light ranging device.
 20. The optical systemfor performing distance measurements set forth in claim 18 wherein thebulk transmitter optic comprises one or more lenses configured as imagespace telecentric lens in which the discrete beams of light output fromthe illumination source through the micro-optic channel array areparallel to each other.